Odd Duplicate Serial Number Error

You know that error that you see when two serial numbers of FileMaker log into the same server? The second copy to log on gets a message that the serial number is already connected to the server and FileMaker quits.

I'm getting that, but in a very odd way I've never seen. First of all, the "server" is a copy of FileMaker Developer running on Windows. The client is FileMaker Pro running on Mac OS X. The error doesn't come up when the user connects to the server as one would expect, but when a particular script is run. This is a multi-file solution and one of the files tracks projects and another stores documents. The documents table is an external data source within the projects file, and this particular script is used to add a new document to a project. The script stores the project's ProjectID in a variable, goes to the appropriate layout attached to the Documents table occurrence, creates a new record, sets the ProjectID for the record and returns the user to the original layout. The error appears just before the New Record/Request script step.

This error didn't originally appear until I added a new feature that didn't even change this script. The new feature allowed the user to open the document, edit it and have the document placed back into the container field when they were done. This worked by first saving the document to the temporary folder, opening it and showing a custom message which, when dismissed replaced the contents of the container field with the edited document. This still works as expected, but after adding that feature, the original script began giving this strange error.

I've never seen anything like this and am wondering if anyone else has.

Thanks,

Chuck