First make sure that Help->About says that you have version 14.0.120.1105 of Money. If it say you have something lower than 1105, somebody reinstalled Money with the original incomplete media. In that case you would reinstall Money using the appropriate
link in the first posting on this forum. If you have 14.0.120.1105, continue.
Copy your problem *.mny file to another disk or flash drive. Then locate your newest *.mbf file. Right click that *.mbf file and do File->Restore of the backup file. If you don't want to overwrite the problem *.mny file in that folder,
do not accept the default location to restore to. Instead, Browse to your Documents folder and specify a filename that does not yet exist there.
If that fixes things, good. If it does not, consider restoring your second-newest backup file. If you don't have another fairly recent *.mbf file, consider your backup procedures if you get Money working again. Then see if you can make a repaired version
of you *.mny file with File->RepairMoneyFile->StandardFileRepair level 2. It is unlikely to fix a problem presented as a password problem, but it seems worth a try.