Hello World ! I can pretty much deduce cause and effect here, although
I can't yet tell you the process.

The Microsoft 2nd Tuesday patches rolled out in October; by Wednesday
there were people that couldn't log-in: SOLUTION: 5 reboots. This
solution worked on at least 10 of my 55 machines. The rest were untouched.
They were all configured the same, except for the presence or lack of
yahoo messenger, similiar programs, and yahoo drive-by tool bars.

Several of the machines continued to have trouble. On some, but not
all, I discovered that Novell Client 4.91 SP2 had reverted to 4.91 SP1.

I re-installed SP2, as the bugs in SP1 are onerous. We are an
Autocad/ABS/ADT shop here.

The logging in problems went away after an hour of trouble-shooting.
Now everthing is happy.

-=Dick Simmons, CNE