Spatial References

Hello. I am working with a file gdb that contains about 107 feature class and 12 feature datasets. The problem that I am having is that from time to time if I try to move a feature class from one dataset to another I receive an error saying spatial refs do not match. I have checked and everything is identical. Is there anything I can do to make things right?

I am using 10.1 sp1 desktop advanced on XP pro sp3, but have also run into this using 9.31.