Ok, I went to Acc Management. It says his forum account is 'Active' and that 'Your forum account serves as your login for the forum'. Then went back to forum login and it still doesn't work. He has never created a forum acc so why does it say 'active'?
Should be working then.. All I can suggest is to make sure that if he's on the EU RoM Homepage, he has to log into the EU forums, and if he's on the US/AU RoM Homepage, he has to log into the US/AU forums:
http://forum.runesofmagic.com - EU Forums
http://forum.us.runesofmagic.com - US/AU Forums
You can't log into the US forums with an EU account, or vice-versa.