Contact form broken

My contact form didn't work with my last version - users get this error:

*Internal Server Error
The server encountered an internal error or misconfiguration and was unable to complete your request.

Please contact the server administrator, [email protected] and inform them of the time the error occurred, and anything you might have done that may have caused the error.

More information about this error may be available in the server error log.*

But I upgraded to 1.3.7.1 and it worked before I went live. Here's the kicker. The error is back. Where is this error log? :unsure:

This is probably a 500 internal server error and is in the log that only your host can access.... try contacting them with the error and see if they can determine what is the issue