OK guys (and gals).... Heres what u due..
1. Open his PM and hover your mouse over his name, then click 'ignore'
2. At the top left of the PM you will see a button that says "LEAVE" as in leave the conversation.... click on that and a dialog box comes up to ask if u want to receive future messages from that person... Click NO (or the approriate choise)
3. Congrats, you have just banned him from your inbox! And from your forum experience...
(the mispellings may or may not have been intentional... )