Had a big problem the other week when one of our databases was throwing heaps of exception email errors on scheduled tasks. After debugging for a few hours I worked out that the transaction log was completely full!
Check out this useful article; http://msdn.microsoft.com/en-us/library/ms175495.aspx
A useful tool is running the following command; backup log
It’s also suggested you do a Maintenance Plan Wizard - http://msdn.microsoft.com/en-us/library/ms189036.aspx
I’ll post more in this when I’ve actually done it 
