It's been a frustrating week so his is submitted with the hopes of helping others.
OS Linux 2.4.20 kernel
Notes 5.011 through 5.0.13 tested
Error message always similar to:
Fatal Error signal = 0x0000000B PID/TID = 10891/16384
Freezing all server threads ...
doing an "lsof -p" of the pid (10891) will reveal the agent of notes which caused the freeze (in our case AMgr) and will identify the database which was being processed by that pid.
Ironically in our case it was the MTBF.nsf database which caused the failure. However, it took us a week to identify it until we discovered that looking at the process by doing an "lsof -p pid#" identified the database.
I hope this helps others!