So, my character was repeating a single-player instanced mission called Nightmare in the Dream Palace and fell through the architecture. The large tunnels in the sky you can see there are different sections of the mission. What's supposed to happen is that you get to the end of one then it teleports you to the start of the other. There are more than just the ones you see here, and although I do have pics of the overall set-up (with rooms floating in thin air, that kind of thing) I had to pull back so far that you can't really see the details.
As a result of this bug, I managed to skip four or five tedious sections of the mission. Ordinarily I'd be pleased, but as I'd only done the mission specifically to try something out in one of those tedious sections, I was a bit miffed.
Oh, and by the way, Funcom, if you don't fix that minor exploit I told you about soon, someone else is going to find it who isn't able to keep a secret...