Are you connecting to FileMaker Server with FileMaker Pro to modify the database accounts? Or are you opening the file directly with FileMaker Pro?
Opening up the file directly with FileMaker Pro while the FileMaker Server is hosting the file may corrupt the file.
If the file is still open in FileMaker Pro and the server has yet to open the file, the FileMaker Server will not be able to open the file.
I am using filemaker pro to connect to the database on the server. I open the database using the file/open remote feature. I then add an account, and the next time the database is closed on the server I get an error when I try to open the database:
Unable to open database "database" (808)