Puzzle: Relationship with global works on dev machine and some clients when hosted, but not others

So here's a relationship that has worked fine during development, but fails when the file is hosted on FM Server and clients access the file:

ID = Order ID

AND ActiveDate ≥ First day by licence

AND ActiveDate ≤ Last day by licence

When I say fails, I mean that starting from a layout of the left hand table, no related records from the right hand table are shown, despite the fact that the relationship graph shows the "crows feet" icon at this point.

The ActiveDate field started out as a Global Date calculation = Get (CurrentDate). Having looked at some forum threads, I then changed ActiveDate to a static global date field and populated it when the client opens the file. But the relationship still doesn't work.

Or, to narrow things down further, it doesn't work for some clients but does for others. In the office network here we have two clients running on Macs, both FM Pro Advanced 11.04 - one sees the records, one doesn't. HOW IS THAT POSSIBLE?!

Any suggestions?

W.