Interesting Mail behavior

[Preston Black]

Yesterday I had an interesting problem with Mail.app. My .mac email 
account just stopped working. I have another account and was getting 
mail from it, but my .mac account was missing in action.

I checked to see if I had taken it offline but I hadn't. I restarted 
and my .mac account's mailbox was gone. I looked in Preferences and 
noted that (inactive) was written next to my .mac account. I went to 
the Advanced tab and checked make this account active. When I did this 
I got an alert saying that I had to enter a username for this account. 
I went back to the Account Information tab and noted several things. 
First, Email address was empty as was the username. And they were both 
grayed out so I could not enter information. Nothing I did would change 
this situation.

I solved the problem by removing this corrupt account and replacing it 
with a new one.

Has anyone else seen strange behavior like this?

- Preston