Win2000 Server SP4 suddenly dropping SMB connections

[Saah]

Hi,

I am experiencing strange problems with my DC, working temporary as a
fileserver.
It serves files for profiles, homedirectories and group resources reaching
about 180 client sessions at server service.
Whenever sessions' count appproches 110-150 connections it suddelny drops
them.
The system resources seem to be quite stable and healthy- 2xCPU at 20%, free
physical memory
at about 64MB, every disk time below 15%.
Once server gets stuck it keeps on dropping conection every 1-5 minutes and
after half an hour
it does not accept connections at all.
The only way to bring it to life is to bounce it which is not comfortable in
production.

When I tried to restart Server Service, I received Error 2019 in Srv, which
made me think
the trouble is somewhere in pool page leakage. The monitoring did not expose
any problems of that kind.

I disabled all Symantec Antivirus and CA Arcserve processes (Start="0x4")
and I am out of ideas
what could cause such as behaviour.

Anyone experiencing the same?
Any ideas?

Been there, seen it:
http://support.microsoft.com/kb/822219
http://support.microsoft.com/kb/317249
http://support.microsoft.com/kb/285803
http://support.microsoft.com/kb/311563
http://support.microsoft.com/kb/312362

 

[Saah]

Further analysis showed that in fact all the sessions remain connected
while open files are zeroed in "net session".
Meanwhile perfmon draws "current clients" peak up to 600, "Server Sessions"
grows about 25%,
"Files open" remain stable or even gets smaller.
In about 2 minutes time all grown "Current clients" gets back to the
starting value (about 138)
and "Files open" hits zero.
From that point everything acts as if the server is right after a start.

The problem returns in 30-45minutes time without any noticeble pattern.
Any clues, advices?