I don't think anyone is doubting it happens, but for the record here's a video I made a few days ago when this issue crept back up to the top of the lava feed (no idea how to embed it).
http://www.screencast.com/t/e8szIGbKRz
Doesn't show much, just that it happens. I sped up time during the video, but it was a few minutes of me trying to add a numeric control to a class. Got so far as to add the control and attempt to change the name. I had to kill LabVIEW.exe before I even got a chance to change the control to an I64. By the time I produced the video I had let the IDE spin for about 20 minutes before killing it, but I've let it go overnight before and it has not recovered.
The ridiculous thing is when I went and edited the class alone, I then went back and opened up the original project and everything just worked, no big recompile times once it had to load the modified class. This is fairly typical when this happens.
The class in the video is very simple: it has no VIs except accessors, all are static and available through property nodes; not involved in any inheritance chains (except LabVIEW Object); and I'm pretty sure none of the fields are objects so it ought not to have any class dependencies.