Mail Will Not Quit and causes finder to hang.

Question

Yesterday my mail app started to give me the spinning wheel while receiving new mail and will not quit no matter how I try to force quit. This includes forcing a quit through the activity monitor, force quitting through the finder and right clicking > force quit. It has since continued and now in its wake other apps have started to randomly hang as well. Even Thunderbird has done the same thing a couple times. Up to this point I have never had any issues with Mail.
I removed any third party add-ons from the bundles folder and no improvement.
I copied the mail folder to the desktop from user/library/ (Which causes the finder to hang but appears on the desktop once I relaunch the finder. This also happened when I copied the mail preference file to the desktop as well)
What the **** is going on here? Should I be worried about worms at this point? Could one corrupt file affect the system this drastically if it is indeed a corrupted file i received?
Anyone have an idea what might be happening here? I really am trying to avoid reinstalling system software here as I have no idea if re-importing my mail folders will yield the same problem.

Answer 1

The new info is really important, and I am glad you reported it. It sounds very much like something corrupted preferences for Mail, but interesting if only one account was lost.
With what you call you secondary account, have there ever been any changes made by the provider, such as a change in server names that you made as an update to account set up info? When that happens the account folder does not get renamed, and when preferences are lost, and you set up as though new, the old account folder is no longer recognized.
Were you using any applications that could have temporarily used nearly all available disk space in some session of work?
I think you need to purge the preferences file for Mail, but we need to know what may be needed to reconnect to both account folders.
Quit Mail, and in the Finder make a Duplicate of the Mail folder that you found in the Home folder, and drag the copy to the Desktop for temporary backup. Next open Home/Library/Preferences and find the com.apple.mail.plist file and either delete it or drag it out to be on the Desktop.
Relaunch Mail, and set up your accounts again, and decline to import anything even though prompted, and Mail should if all else is well rediscover both account folders.
Please keep us posted.
Ernie