Thunderbird is causing trouble

I keep having trouble with Thunderbird. Right out of nowhere I got about 200+ new emails in my inbox marked unread, but they were emails I read and had deleted at least a year ago. Sometimes when I try to make Thunderbird check for new email it either says there is no new email even though I can see it via the gmail inbox on a webpage, crashes, or keeps giving me emails I had already recieved and deleted from the past. It's really getting annoying, and it's doing it even after I un install and reinstall. How can I fix this? I keep thinking I'll have to turn to the dark side and use Outlook Express.