Is this on the same machine as it was running before?
Technically this is the recommended route by requesting a support case... Lower left of the page.
http://www.ptc.com/communities/academic-program/technical-support
If the licensing process included getting a MAC address of some sort, it is very easy to get something oher than the actual, physical network card's address. Also problems in how they are listed in your registry can cause havok. Maybe it is stuck trying t read the old license. I'm just guessing here since I run the full version, but this is a very common problem although manifest differently.
