Bulletin board went down

i was using ULTIMATE BULLETIN BOARD made by infopop.com for years now…i had it uploaded into my server… and now for no reason at all when i go access my guestbook i get this error listed below. how come?? it worked for years and now the guestbook won’t even come up…i know i have a perl enabled server and i never touched a single thing on the guestbook…any suggestions on why this will happen on it own?

“Internal Server Error
The server encountered an internal error or misconfiguration and was unable to complete your request.
Please contact the server administrator, webmaster@theknowhow.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.