If you are on windows, they have a Mail app, it's part of the Windows Live stuff. You can try that. http://explore.live.com/windows-live-mail

Though I find it hard to believe your assumption that updating two separate programs at the same time was "crossthreaded" (whatever that means in this context). Just remove them and reinstall the current versions. For your imap accounts, all the messages are stored on the server, so even if you have to recreate the accounts in t-bird, you haven't lost any mail messages.

chrome is worth trying either way. But there's no reason you can't have a cleanly working firefox also. Get rid of all the plugins and do a clean install.

-David