Huh, bard mez is pretty funny. When an enchanter mezzes herself, she can count on it wearing off after a certain amount of time. When a bard mezzes herself she will continue to do so indefinitely as it pulses, until she finally resists it two times in a row, and then interrupts her singing quickly enough to prevent it from pulsing again.
I found this out painfully the other day with the Ancient Mez (which contains a HUGE MR resist check - making it very difficult to resist). Let's just say that I saw after 5 minutes of panic that the only way to reverse the problem was for me to /ex out and log back in. =(
Props to Ryst for keeping three mobs on ice for almost 13 full minutes (I checked my logs, I'm not exaggerating) while I figured out what was going on, /ex'd out, and logged Allie back in.
One thing I noticed at the time was that even though I did get a message saying the mez had worn off, the icon was still there and I was still mezzed. In addition, it wouldn't have made sense for my mez to have worn off since I didn't get the resist two times in a row. My only guess is that I got a message saying it had worn off only because it had been overwritten by the new pulse (although I don't get those messages with NPCs)
So, that was a pretty embarassing story to air in front of all y'all, but hopefully it will help you guys figure out what the problem is. I'll try not to mez myself in the future =/.