I upgraded VM just last night and now my site is knackered. (2.0.20b)
Have you upgraded to the latest Puremart? (but wouldn't think that this had anything to do with it)
What was your VM version before?
Have you a backup?
Have you checked for javascript errrors etc?
Upgrading VM overwrites EVERY single file in your VM install - all and any custom work will be lost..
But as it is the upgrade of VM that did it I'm not sure why your asking here....
You can test without Puremart..
You can temporarily disable PureMart by changing the name of this folder from:
ROOT/templates/<yourjoomlatemplate>/html/com_virtuemart
to
ROOT/templates/<yourjoomlatemplate>/html/com_virtuemart2
and set any over-rides back to default
But in the short term I would roll VM back and test an upgrade on a seperate test install before touching a live site...
Cheers