Thanks for the reply, I tried that and it didn't effect the problem.

It's definitely something to do with automatic mapping, I tried creating a brand new simple Poly sphere (in a completely new file), and when I mapped the UVs using "Automatic Mapping" I have the same problem!?
I've tried resetting the default settings for the automatic mapping feature to no avail.
It may be that this is some issue with my system and Maya 7.0.
I was trying to remember, but I don't think I've used auto mapping, since I upgraded to 7.0 (though I used it quite often in 6.0 without any problems)