I'm just getting back onto this forum now, and noticed some threads on spam in the suggestion box forum, then I noticed 2 new spam accounts in the past few hours, so it seems to be an ongoing problem.
This might be a bit late coming, but http://www.phpbb.com/community/viewtopi ... 1&t=427852
seems to be a good resource for getting most of the bogus accounts under control.
I know what a thankless task running a forum can be, both for the admins and mods, as I've suffered through admining MyBB(4 releases in 6 days due to exploits).
If you haven't already read this info, I hope that this makes your job a bit easier.