Force Close Error on T-Mobile myTouch HTC 4G

I used T-Mobile myTouch 4G by HTC with Gingerbread OS. I got this error when using the Mail App. I can access my mails but I could not open any attachments. I am under charter.net when I received this error. When clicking on Force close, the Mail App will close. Can someone help?

Sorry!
Mail has stopped unexpectedly.
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