Dear George,
Do you know if your database is running in Simple recovery model or Full recovery model? You can find this out by opening management studio and right clicking on the database itself, and look at it's options under properties. If it's in a Full recovery model, it probably hasn't taken a transaction log backup in a while. If it's in Simple recovery model, you may have run out of space on the disk or you hit the maximum size set for the transaction log file.
A situation like this would be best handled by your DBA. However, if you don't have one, and all the above sounds obscure to you, it would be best to open a support issue with your first line of support and they should get you the help you need. Our Tech Support team can respond to you faster than the forums.
Hope this helps!
Brad
