Additional instances cannot be launched

I have managed to run normal Wotlk instances. But today I noticed that after we broke up I "couldn't launch an additional instance" when I went to the instance to recover my body. So I wasn't in the group anymore and I didn't want to get a new instance, but it tried to launch one anyway. So how many instances have been launched in situations where people actually don't really need one? Maybe people just go to check something or go fetch their body or something and that wastes an instance? If there is a group wipe and then the group breaks up, and everyone goes get their body from the instance, that group just wasted 5 instances...