...as you probably already know my projects run EXTREMELY slow...
Not sure how I'd know that, but in any case the universal equation goes like this:
RoboHelp Project on a network = S L O W (and hazardous to the project's health)
If you really need collaboration, you need to investigate a Source Control system. (RoboSource Control, PVCS, StarTeam, Visual Source Safe, etc.)
Helpful and Handy Links
Or, simply use the shared drive as the repository for the project source files. Then each of the writers copy down the latest version for editing on their local machine. Each of our projects were exclusive to a certain writer, so there was never an issue with reconciling dueling versions.
We did it that way for over four years, until we started using the RSC product bundled with RH8.
Whichever method you choose, the same protocol applies as Rick said: