[NOTE: I posted this originally at StackOverflow but it got no traction there - reposting here.]

We have a bit of software installed at a few client locations that runs (via Windows task scheduler) a few times each day.

In ONLY ONE of the client locations, we have a unique problem: each month, the task will stop working, after running every day for weeks. Twice now it's failed on the 2nd of the month. When I walk the client through troubleshooting it, we've found that it can't start - access denied.

To fix it, we simply re-enter the same exact password, and then off it goes happy as a clam.

I've never heard of this issue, and their IT people say they don't have anything running once a month that might cause that.

I'm at a complete loss here. Any ideas as to why this might be happening?

Further details:

Windows XP pro machine. Task is being fired with credentials from a local admin account. Computer is always on, and connected to the net.