Hi!
I am not sure how you set up your project files but here are some guidelines.
When working in semi-isolated environment, the point is that you should only work locally when editing a part. You use the check out process to place the part locally. All other parts in the assembly are still on the server. (All other users can then see if some files are checked out or not.)
Suggested; create a *.ipj file which is placed on the server. That file should contain a workgroup with all wanted paths, and library search-paths if you have any. Then every user should have their own projectfile with their own private workspace (locally). That projectfile should have the server *.ipj as an included file.
When I read what problem you have, I am almost certain that you have some missing paths in the projectfiles.
/Pep