Cookie_Number is a unique postfix given to all of the cookie names. It's assigned randomly to the board during initial install, and is used to allow multiple installations on the same domain name. Without the postfix, there'd be some pretty interesting cookie conflicts.
As for the PM funkyness... there used to be a utility that can rebuild PM indexes, but I dunno if it's still available. However, the very fact that there was corruption present tells me that your board has some bad mojo...