I get the same thing. Well sharing a project is more complicated. I still have a version of the project in the shared folder, but everyone has to save their changes in their user first, then copy that to the shared folder. Overwrite the file in the shared and so on with each user. This is more of an OSX question. But this has been my work around.
Hope this helps-
Matthew
Quad 2.5 G5
OSX 10.4.X
Ram 4GB
FCP 4.5/AE 6.5/DVDSP3