Would you freeze a cake after it's been covered? And if you do, is there a trick to thaw it properly?
Any tips or advise would be much appreciated!

I found this link very useful, it should answer all your questions. I have no experience in this though, so can't vouch for the success:

http://www.ehow.com/how_5562675_store-fondant-cake.html

i've frozen two of my fondant covered cakes-and only because they wanted pick up at a later date (change last minute) i did tell them it was frozen. but you know what, turned out awesome. trick is to make sure it is securely covered, multiple layers of saran not touching the fondant. uncover when removed from the freezer, and make sure no body touches the cake as it thaws. (fingerprints show!!) but works great.!! in my experience. HTH

sorry some clarification-yes Saran Wrap, i usually rip off a large piece and gently cover the cake making sure that it dosn't stick to the cake, but is secure to the cake board or the bottome of the cake.
make sure your fingers do not touch the cake when you remove it from the freezer as you will leave finger prints on it!!

it would have to stick to the cake in some places, surely? It's hard to imagine plastic wrap behaving itself and floating around the cake? Or do you just mean try to avoid it as much as possible? Maybe it would not stick if you used a few layers to make it thicker and stand up more..?

Yup that was exactly what i meaning to say!! thank you!! sometimes it's hard to explain!! i did put multiple layers on that ended up being thick therefore not actually really touching the cake too much.

I had to freeze a fondant covered cake because the client changed the date of the party without telling me.. aaarrgghhh! I put it in the box and wrapped the box several times in saran wrap. When it came out, I just took the wrap off and left it in the box to thaw. Turned out awesome!