Sounds like an opening script may be looking for some verification between log on name and user name or account name or the PC's ID.
Thank you for your post.
The answer by TECman is the likely cause (Thank you!), but since you are not a FileMaker expert, here is what you need to do.
Launch the file with FileMaker Pro, pull down the File menu and select "File Options..."
Click on the "Open/Close" tab (if not already selected), and there is probably a check next to "Perform script:"
Click on "Specify", and write down the name of the Script that is highlighted. Click "Cancel" twice to return to the file.
Pull down the Scripts menu and select "ScriptMaker..."
Look through the list of scripts for the named script and double-click it. This then gives you the script steps. This is where you would determine what is happening. Feel free to let us know what are the steps, and someone here will give you some guidance.