OS Lion Mail: Microsoft Exchange Server Rejects Password

Hello,

I just upgraded to Lion and was attempting to set up all of my email accounts into Mail. My Yahoo, AOL, and Gmail accounts all worked fine, but my Microsoft Exchange account did not. When I set it up through Settings originally, everything seemed fine and it had no problem verifying the account. However, when I try to retrieve mail from the Exchange account within Mail, it gives me an error saying that the server rejected the password and then prompts me to enter the password again. I enter the correct password, and the same window pops up over and over again. Has anyone found a fix to this problem?

Thank you!