SeMain20 consumes 100% CPU resources

I have 3 NT4 Terminal Servers with sp6 and Citrix Metaframe 1.8 with sp2 loaded. At randon times, and servers, SeMain20.exe will consume up to 100% of the 2 processors that the servers have; leaving no other choice but to wait for almost 20 minutes or reboot. Any ideas on this enigma? (This system process cannot be killed)