Domino 6.5.4, SMSDOM 4.1 & SAV client 10.0.1.1000

This is our onfiguration:

Windows 2K3 server
Domino 6.5.4
SMSDOM 4.1
SAV client 10.0.1.1000

We have excluded all directories as listed on the symantec support site and have
created a new temp directory for SMSDOM. Everything seems to operate
ok, except for scheduled scans. Whenever a scheduled scan starts it
takes very long to finish or does not finish at all. I installed the
SAV client about 5 weeks ago and before that a full scan only took
about 3 hours (for 40 GB data). Nothing else changed in our
configuration.

I found some posts about this but no real solution. What can be the issue here?