HTTP Error 401.1 - Unauthorized: Access is denied due to invalid credentials

I get a call this morning that one of my applications isn't working. I go to check it and sure enough I'm getting the following: "HTTP Error 401.1 - Unauthorized: Access is denied due to invalid credentials". This application impersonates a specific Windows account so I check the usual stuff...

• Password change : Nope
• Security on the filesystem: All set properly
• Long username problem : Nope, not the problem here
• Account Disabled: nope

So, I'm running out of ideas.. so, I try to recycle the App pool (smart me, created a separate application pool just for this particular application). The pool comes back online and still no go.

I start looking through the log files and I'm not getting any more information except for the "invalid credentials". I take a look at the account again and chuck it into domain admins just to get this up and running. Recycle IIS this time and poof... same error

So, I've now ruled out any possible unauthorized access issue. So I take one final look th the user properties and I notice that even though the account isn't locked out, the password has lo and behold expired. Then I notice that the checkbox for "Password never expires" is not checked. I check the checkbox, apply the changes, and poof.. everything works

So, the lesson here, boys and girls, is to make sure you make sure your service accounts passwords do not expire