ora-03113 end communication channel

After my client upgrade from NT domain to 2003 server/Active directory, the user start having problem with the connectivity to the database, they are on 9i /windows 2000 server. The user was able to log onto the database and randomly (after a few minute) they got ora-03113: end communication channel.

Does anyone have this issue before??? How do I troubleshoot the issue??? turn on the trace on the client level???

ORA-03113 is a tough one. There's stuff on MetaLink and a collection of cases here: http://home.clara.net/dwotton/dba/ora3113.htm

I did have genuine network probs with WinNT4 SP4 (TCP/IP stack handling probs), which gave ORA-03113, but they went away with SP5 - ancient history now. Worth checking if there are SP's for Win2003 that deal with IP probs.