#1 404 error

[Mist1]

Having an issue: tryed upgrading to latest version, and checked all permissions. Everything seems fine -
Getting the following:

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

Please contact the server administrator, webmaster@uwbtec.com 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.

Additionally, a 404 Not Found error was encountered while trying to use an ErrorDocument to handle the request.

--- Doesnt matter if I go to admin page, get the issue there, also when I click submit on the form. No data is going into the MySQL ---- The table, and fields are correct, cretaed by phpform.... Username, Password, etc are all good. Any suggestions?