The passwords are part of the database file. If you transfer the file, the passwords come with the file. Filemaker 7 through 11 use the same file format so you haven't even changed the file here during the upgrade from 7 to 11, it's exactly the same file.
If you had FileMaker 6 or older and converted to FileMaker 7 or newer, the file converstion alters your file in many ways. Instead of a single password, you now have an account name and password. To open the converted file, enter your original password twice, once in the account name box and once in the password box. Once you have the file open, you can go to mange | security and change your account names so that other people can't see the password you are entering as the account name.
Also, keep in mind that passwords were not case sensitive in FileMaker 6 and older, but are case sensitive in FileMaker 7 and newer. If you still have trouble opening the file, you may want to open your original filemaker 6 or older file in FileMaker 6 or older and check the capitalization used when defining the password.
If you're using the Mac "keychain" to remember your passwords...well, that's a Mac issue and you'll need to research whether there's a way to transfer your keychain settings from one machine to another (I doubt it). But as Phil said, FileMaker's passwords are stored in the database file itself and don't get lost when moving between machines.
Thanks all. I solved the problem, it was the account name that was wrong not the password. Your clues helped me.