We have two licenses for Visual Assist on two PCs running Windows 7 64 bit and were very happy. One thing I have noticed is that when my colleague and I swap places and log in to the other PC as ourselves, we are no longer licensed. This seems odd.
For VS2010 Visual Assist X is installed for the current user only, not for all users on the computer, so this might be a factor. If you enter the license key, is it remembered?
You should not need to reinstall VA, it should already be installed for all users of VS2008. What exactly is happening? Is VA not installed at all when you change users? Is it installed, but not licensed? Something else?