Heck, I have that dream all the time. Even now, years and years out of school. Usually I want to go to see the teacher of the class I haven't attended only his or her office door is bricked up, or I wander through the building (it's the same as it was when I was in college, not as it is now) and can't find it.

I figure that it's just my unconsious mind working something out. I have other recurring dreams, too.