samba - Nov 2003 - Directory access works, file access does not

Hi list,
I'm sure it's an old question but Google showed a lot of problem
descriptions
but no answer to my problem...

I've got SuSE 9.0 with Samba 2.2.8a running on an athlon 2000. The 
Samba-Server is member of a NT4-Domain, the Clients are W2k. The users can 
browse the directories without real problems, it seems a little slow though. 
But if one tries to open an arbitrary file the Windows Explorer hangs for a 
rather long time (about 1 Minute). Then either the file finally opens or 
there is no - absolutely no - reaction at all. I sometimes thought, I might 
have missed the mouse botton...

I tried to log the attemts using different log levels, but the results are 
inconclusive at best... Sometimes Samba logs a message:
read_failure: read failure for 4. Error = Connection reset by peer
but even that happens only sporadic.

The funny thing is: An old SuSE 8.0 Box running samba 2.2.3a works better 
although unreliably - spurious kernel panics during file accesses led to the 
upgrade to the above machine...

Here is the global section of smb.config of the new server
[global]
   workgroup = MyDomain
   netbios name = P230408
   comment = Keine Backups, max. 250 MByte pro User
   os level = 2
   guest account = nobody
#   keep alive = 0		was a suggestion from Google
   keep alive = 30
   kernel oplocks = false
   character set = ISO8859-1
   username map = /etc/samba/smb_user.map
   client code page = 850
   valid  chars = ?:? ?:? ?:? ?
#   time server = Yes
#   unix extensions = Yes
   encrypt passwords = yes
   map to guest = Bad User
#   printing = CUPS
#   printcap name = CUPS
#   SO_KEEPALIVE=0 was a suggestion from Google
#   socket options = SO_KEEPALIVE=0 IPTOS_LOWDELAY TCP_NODELAY
   socket options = TCP_NODELAY
   wins support = No
   veto files = /*.eml/*.nws/riched20.dll/*.{*}/
   security = server
   password server = 192.168.20.1
   server string = File Server
   add user script = 
   domain master = false
   domain logons = no
   local master = no
   preferred master = auto
   load printers = no
   interfaces = 192.168.20.237/255.255.255.0
   wins server = 192.168.20.1
   log level = 3

The commented lines are suggestions made by others and tested without success. 
I can post logs if somebody tells me what log level should be used. The logs 
tend to grow quickly with increasing loglevel ;-)

I hope, somebody can help me with this problem - thank You

Roland