Server is Win2k SP4 running BUEX 8.5.

I have one database out of four on a SQL server that locks up when it is
backed up. All the other db's on that server get backed up successfully.
The last db's is the problem db. The error log for BUEX is "The database
server is not responding. Backup set aborted." The SQL server indicates that
the backup is still running even after BUEX states that the job has been
aborted. I have to have the SQL dba go in and manually kill the job on the
SQL server. Any ideas why this is happening?