Does NewAdmin also use '!' commands? If so, that's definitely the cause.
Megiddo, yes, it does. Badly.
@Orangeez;
NewAdmin is a definite problem. No idea of PCmod 2 (not heard of it blocking)
Overv blocks all other "!" text commands/all other mods within NewAdmin. He returns false if the ! text doesn't contain text of his commands.
Not only does his script block other chat commands, it has a timer that checks if his function has been broken, and puts it back if it has thereby breaking all other chat hooks even if they were the one to break his.
I've no idea if he ever fixed or allowed for changing of the chat prefix. Not sure where you got yours, or if it's the latest. I thought NewAdmin development had stopped; which I'm glad.
Side note; I never mind competition to ULX. I strongly dislike Newadmin and Overv for his 'I'm better than every other mod out there' attitude, yet his code usage such as this bad use of chat hooks proves it isn't.