License error, code=-4

According to the forum, code=-4 means the license has expired. However, a faculty aide in our university uses the same license and we also had him do a clean install and he doesnt encounter the same error. We have an academic license and we use ArcGIS engine 10. Our license expires this month but no date is specified and, as stated, someone else can still use the same license. I have tried installing with other machines and the case is the same. Thanks in advance!