Okay, I promised y'all the story.

I got home from work 9:00 pm that night, we had a passenger who needed to be delivered. While we were there they invited us to dinner the next day around 5. (I would be on 9-3). Could we bring deviled eggs? (They are quick and easy - and everybody seems to like my mayo/mustard/butter/ eggs). He said it was to bad we couldn't bring a cake as well, since I had just completed levels 1 &2 in Wilton decorating.
Thought a minute and - yeah, I got a double handful of mixes for when 3 goes off, or if I do fondant instead wheil tryihng to get 3 going... have mix, if we do shredded coconut on top for grass, jelly beans for eggs, brown basketweave to make it look like a basket.... it can be done.
So we stopped at the store on the way home to get coconut and jelly beans, got home at 10, threw eggs on to boil and a red velvet cake into the oven. Turned it all otu to cool and went to bed.
got up, started shelling and deviling the eggs, mixed standard buttercream recipe, using margarine rather than lard since it would be eaten that evening. Went straight to Med consistency since I wold not be doing standup on this one. It was a wonderful soupy thin. I frosted the lower level of the red velvet, put the top layer on and started to ice - the top layer broke into 3 pieces (this is all at 6 am, you understand)
Okay. Look at clock and cake - there is time to do a yellow cake...and enough supplies to try the icing again. This time it was margarine and sugar without anything else other than 1 tsp flavor.
Thin straight from teh get-go, so I started dumping pwd sugar in to try to thicken it up. Got a usable consistency, quick iced the top of the yellow cake layers - sides would be woven and time was short so I didn't bother there.
kept thickening it (maybe 2 more cups of sugar? maybe 3? I wasn't measuring, I was dumping) it finally looked like it would hold - no time to ice, so I threw it in a covered bowl, stuck the deviled eggs in the frig and off we went.
Got home, the frosting is still soft - threw in some more sugar, threw in some green coloring (well, blue coloring which went green on me due to the margarine I had used), and started weaving - got two verticle slats, caught it on the spatula as it slid off, tossed it back into the bowl - more sugar dumped in.
Finally got it solid enough to mostly hold (one section was still slipping), did a fast and dirty weave, quick braided rope border on top, fast shell on the bottom (default when I'm tired or in a hurry), forgot to ice the board - (ahd put the coconut on before I went to work that morning, showed him how to attach the "eggs" and left him to it so all I would have to do is finish it.
WE got it out, there were oohs and aahs (and that one section starting to slide south again) - put it on the cake stand. One of hte other quests managed to make room in the host frig (I don't root around in someone else's frige) - and we put the cake there to keep it from melting worse.

learned later that hte main register was right where the cake was.

Thinking on it, the problem with teh icing is that margarine has a heavy elelment of liquid in it to start with, to keep it soft; perhaps if I start with stick butter next time, rather than tub, I will have success with this form (but oh, the taste of true buttercreme, rather than mock!)

thoughts and suggestions on what I could have done differently.
(on the velvet, neither layer was smooth - I flipped one, mated the dips to the humps. I think the main problem there was the cake was not completely done, so when it failed to have solid support it split.)
The final cake was uploaded under Easter Cakes.

http://www.cakecentral.com/modules.php?name=gallery&file=displayimage&pid=1203429
a link to the cake I finally achieved. I know I'm doing the artist thing (I always do) and seeing only the faults. but...I need to continue experimenting with that butter icing. I know it comes out good because the first time I made it I was 8 and my little brother was 4 - and when we got done, we had an inch of icing on the cake and 2 boxes of graham cracker sandwiches (it's to thin, needs more sugar. it's to thick, needs more butter, it's to thin....)

LARD in your icing?

that's number one, lol

also, margarine is a chemical compound that is meant to stay soft. It has been reborn in the new forms that look closer to a butter stick than the older ones, but it will never get hard on you.

Also, the heat of the mixer will make is soft and thin.

The friction of your beater whipping around is creating heat and keeps the marg. in a sort of melty state, that's why you were having such trouble.

Why don't you just use a stick of real butter, that should get hard as a rock as soon as you refrigerate it, and probably tastes better too.

You should always use butter or butter/shortening or just shortening in your BC. The cake was cute, even with your mishaps
I can't say I've ever added lard to my BC before , did you learn that in your Wilton class?

I tend to interchange lard and Crisco when I speak, even though they are two entirely different things (Crisco is fake lard, after all)

does it take more cooking to get Red Velvet cooked than most? This is the second one that had to cook longer and still didn't have the right interior consistency (third hand stove with a faulty door does not help matters any, either, but right now there is no buying a new one - and we rent)

I always use half margarine (sqaures), and half crisco... and I usually have to add water to thin it out in order to spread it.

I've usually use a 50/50 mix of margarine (stick version, not tub) and shortening and get a nice, soft buttercream, but it also crusts and when refrigerated it acts like an all butter buttercream. It sounds like the problem you're having with the margarine is because you're using the tub version, which has more liquid in it and is made to stay soft, even when refrigerated. I don't think you'd get a good stiff buttercream from tub margarine alone, no matter how much sugar you add -- and then you need to worry about having it too sweet. I've used stick margarine alone for a creamy chocolate frosting before, but even that is too soft to really decorate with. If I want to decorate with it, I always cut the amount of margarine down in half and add that much in shortening back in.

Not really sure about lard .... I've only used that in pie crust, but don't even do that on a regular basis.

a 1/2 and 1/2 American Buttercream is actually pretty nifty tasting!

true - lard is hardened animal fat, and Crisco/hardened vegetable shortenings are vegetable oils that have been hydrogenated and other things to give them the appearance and consistency of lard.

I called it fake lard because the reason shortening was invented as to replace lard in all those recipes in the 50s and provide a "healthier" alternative, just as margarine was invented with the look, feel, and supposedly taste of butter to replace butter with a "healthier" alternative.
I say "Healthier" because there is still argument as to whether they really are or not, and those arguments will still be around when the sun goes nova.

But that was my thought to - margarine is designed to stay soft and spreadable, and that was where the original problem lay...but there was no time to run out and grab some sticks. May start converting over though, since I use it for cooking and shortening, so there is no real difference from my point of use between the two forms!

This proves you *need time* to create a nice cake.
It can't be 'just thrown together at the last second'.
There are many, many, many recipes on this site and others for a good icing that WILL make decoratiing easy and they take far less time to make than what you did
BTW: I never ice the board. When it's covered w/something that resists grease it can actually compliment a cake's decorations.

it could have been thrown together if I had the right kind of butter in the house - but that is what beginnings are for - to learn and move on! The actual decorating, once I had usable icing, only took about 40 minutes.
and if you don't know what went before, the cake really doesn't look bad (aside from the one or two gaps where you can see cake through the lattice, but those who were devouring weren't looking for flaws!
And this cake makes my...7th? 8th? decorated cake. The instruction book says you can use butter or shortening, it doesn't specify WHAT KIND of butter! Live and learn, the next one I will pull off.