Chris is correct in that the error is pretty generic. The MethodServer log should be consulted.
Additionally, there are a few articles that address some situations where this error has occurred:
http://support.ptc.com/appserver/cs/view/solution.jsp?n=CS148175
http://support.ptc.com/appserver/cs/view/solution.jsp?n=CS30885
http://support.ptc.com/appserver/cs/view/solution.jsp?n=CS93882
http://support.ptc.com/appserver/cs/view/solution.jsp?n=CS38354
http://support.ptc.com/appserver/cs/view/solution.jsp?n=CS45185