I'm using build 1635 with VS2005. All of a sudden it is giving me the trial dialog. The thing is my support doesn't run out until 2009 and it is even showing up that way in System Info.
and re-enter your license key, or even enter your license key via the button on the trial dialog, does this fix the problem?
Which OS are you running? Are you working in any form of remote desktop / remote server situation? I am wondering if somehow the registry keys for the license key are not being set correctly. This could be down to user priveliges, or perhaps the server "rolling back" the registry.