Being locked out

Greg,

There could be two possibilities:

a). That you are running a batch job that is configured to use your username for running and something seems to be wrong in the credentials that you have supplied (???)

b). May be someone is indeed trying to attack the network using your network credentials.

Some questions before I answer this:

How often do you find this problem?
Do you have sound password management policies in place?
You have mentioned that you are locked out in the evenings. Is there a pattern that you can locate from the Event Viewer => Security logs.
Who could be accessing your SMS server, so as to attempt to connect to your machine from there. is it a critical piece of equipment? In that case, this should not have happened in the first place (Physical security???)
Do you find this happening during week-ends too?
Do you have remote access servers in place??

I am sorry for asking so many questions, but this is typically the investigative path, a person needs to take when he is trying to nab a culprit. Also, needless to say, these questions will help you investigate the matter yourself.

NIST's recent documents on securing Windows 2000 workstations and NSA's guidelines for securing Windowsmachines will serve as great best practices for tackling these kind of problems in future.

Thanks,
--Rookie

PS: Your mail ID is already available to comment so incase you have more questions, I can answer them directly, in case you have any. Don't spend your points for this ;-)