Tab key and Mate References

Has anyone noticed that there is a problem with Mate reference in 2004 sp1: When dragging a part from the Feature Palette (palette part), if the palette part has a Mate References, using the Tab key would allow us to toggle the direction of the part. I am placing studs in a sheet metal part (sub ass'y level). I have tried on 3 machines: the Tab key still flips the part up or down, but when releasing the left mouse button, swx flips the part in only one direction, regardless of the one selected? I've managed by opening the part (i.e. the stud), split the screen and using drag & drop: then pressing Tab and releasing the l.m.b works.