Here are two videos that go over the fundamentals of license troubleshooting. Whenever I WebEx to a customer’s computer, I go through the steps shown in these vidoes. In almost all cases, this is enough for me to resolve the problems.

Troubleshooting 101: The License Server
http://usa.autodesk.com/getdoc/id=TS13737415

Troubleshooting 101: Softimage cannot find the license server:
http://usa.autodesk.com/getdoc/id=TS13780212
Note – this second video was done for 7.5. For 2010, ADSKFLEX_LICENSE_FILE should point to your license server, not to Autodesk.lic.