Sprint HTC Hero :: Mail App / Yahoo POP Account

I've searched quite a bit and haven't been able to find anyone else with this problem.I've been using the built-in Mail app on my Hero for the last month with my Yahoo e-mail account (it's a Plus account, using the POP settings provided by Yahoo)...with zero issues. Yesterday, I noticed that I wasn't receiving new messages anymore. I've got the program set to update every hour, and even when manually clicking refresh, the phone would not download any new e-mail messages from my account (and wouldn't send either). There were no error messages though, it appeared to be synced up (the time would show up next to the sync symbol in the top left corner of the app.I knew my settings were correct, so I figured I would just try to delete the account and set it up again. I selected "delete account" and after giving confirmation, the message on the screen said that it was deleting the account but it never finished. The program wouldn't do anything, figured I'd try to force it to close with my task killer but Mail didn't even show up as running. Next step...shut the phone down and powered it back on. Opened Mail up and the account was no longer showing, however there is still some memory of it somewhere as when I attempt to set it up again it tells me that there is already an account with that e-mail address.I can get around that by setting up a new account and changing one character in my address until all the settings are entered in (and then go back and change it), but I'd like to find out if I can address this problem head on (without a hard reset).