What you mean you have 3.0 ? There is no such thing Version 3.0 (yet)
The latest version of Virtuemart is VM2.6.6 and it works under Joomla 2.5.xx
See here:
www.virtuemart.net/download
All of our products are currently compatible with Virtuemart2.6.xx and Virtuemart2.6.xx works only with Joomla 2.5.xx
For more info:
www.flexiblewebdesign.com/forum-virtuemart-2-template-support/2071-clean-mart-with-joomla-3-2#9489
As soon as Virtuemart3.0 (stable version) is released to public through:
www.virtuemart.net/download
We will update all of our templates/modules and make them compatible with Virtuemart3.x + Joomla3.x
(Currently VM3.0 is under development, and the latest BETA release is VM2.9.8 - but it is beta, and don't install it, wait for the stable vm3.0 version)
Regards,
Support