Yup
Typically, I can't post a reply using the Quick Reply form, the Full Version reply form works most of the time and starting a new thread always seems to work.
But sometimes I get this when using the Full Version reply form:
Server Error in '/' Application.
Runtime Error
Description: An exception occurred while processing your request.
Additionally, another exception occurred while executing the custom
error page for the first exception. The request has been terminated.
That's pretty special, it's going in my "Exception Handling; You're Doing It Wrong" book :-) [edit: my 'Yup' had mysteriously vanished, so I have re-added it...]