Here's one possibility:
FM 7 files have the same account name and password set up that you see used in FM 12. So the same account name and password should work in the converted file, BUT you moved the file and you are using a new version of the software. Either change may have resulted in an installed copy of FileMaker with a different USERname. This is specified in preferences, and also during installation, but when the standard password dialog opens in FileMaker, this USERName is entered as the default ACCOUNTname in the dialog.
So make sure that you are using the same account name as you did on the original computer when logging in or your password won't be recognized.
Yeah I am putting in the same account name and everything. I guess another thing I should say is this other computer is not in the original network that the database came from.. could that be an issue too?
Maybe I can strip the username / password off the db and then try moving it again?
Passwords and account names are stored in the file, so changing the location should not affect the account name and password required to open the file. The only other possibility that comes to mind is that passwords are case sensitive so make sure that you use capital letters for your password where specified for that password, but this seems an unlikely long shot.
Or this a Mac system and you had a "Keychain" set up to automatically log you on with the original computer?
Not being a Mac user at the moment, I forget about that feature on Mac OS systems...