Thanks for the question. There is a registry key for the 'Create Related Object' dialog. The location should be:
Computer: HKEY_CURRENT_USER\Software\ Miner and Miner\ArcFM8\Create Related Object
You should be able to simply delete this key (with the associated dialog positions) on the user's workstation to reset the position. The key and values will then be reestablished when the user then tries to open the dialog again via ArcFM.
Hope this helps.
Thanks for the fast reply. Your solution worked.