Backup Exec 2012 SQL agent brings SQL server 2005 to a crawl

Hello,

I'm running BE 2012 with an agent on a SQL Server 2005 machine running Windows Server 2003 R2. The SQL server runs fine usually but when I run the BE agent on an incremental backup, the server slows to a crawl and users complain about the speed. Normally users put in a customer number and the record comes right up, but when the incremental backup is running the server slows down significantly. Also, the agent doesn't seem to make much progress.

What should I check first? Thank you.

Chris