Crawl account? Is an admin using that account  by chance to logon? While not
necessarily a best practice, have you tried setting the services  password
manually? App pool idents?

I had the same issue a few weeks ago and the customer was using the farm account
in reporting services (hard coded to access a file share). When we changed the
password on the farm account, we didn't know it had been used elsewhere. I'd
check peripheral usage, such as crawl, custom services, and hopefully somebody
didn't use it someplace wonky like reporting services or elsewhere than
SharePoint. More times than not, your symptoms point to the account being used
somewhere it shouldn't have been. Good luck tracking this down.

You could also create a new service  account. While a pain, it would probably
resolve the issue. Then, just disable the old account and see who screams -
you'll find  the culprit.