Random logon --- error

[Guest RAAckerman]

All of a sudden (this machine is >18 months old) the system returns to the

logon screen. It may not return there for 5 minutes or may return there in

microseconds after logging on.

No virus (or at least McAfee and web test find now). No spyware (two checks

as well).

It generally means the computer can't be used, since the logon intervals are

random- 10 sec, 1 sec, 1 msec