Hmmm, it's clearly ticked off about your MFServer class. But it looks like you've dotted all the i's on initial inspection.
Grasping at straws: are you on Windows? If so, I've seen weird problems like this as a result of casing issues in file names. Something to check. Also, MFServer and MFServlet are really close in spelling; might there be an instance where they were interchanged perhaps?