Backup slow/hangs in one folder

Backup Exec 7.3 for NT backs up data sitting on a NW6 SP1 server.

When it starts backing up a folder containing 5074 files the backup rate
drops right down to around 2mb/min (it was around 100mb/min) and takes
forever to backup – we end up aborting the job. I have done a few tests
and we have another folder that has over 8000 files in and that backs up
fine.

I have checked TIDs 10021744 and 10023910 and changed the following
without success:

Dir Cache Allocation Time = was 2.2 sec changed to 0.1 sec
Dir Cache Buffer Non Referenced Delay = was 5.5 sec changed to 60min
Max Dir Cache Buffers = was 500 changed to 20000
Min Dir Cache Buffers = was 150 changed to 10000

Do these look ok and is there anything else I can try?

Thanks.