FMP is still a 32-bit applicaton and can not use DSNs in the Windows 64-bit ODBC control panel. Re-create the DSN in the 32-bit ODBC control panel.
Wim is correct. But note also that FileMaker Server is 64-bit and needs to use the 64-bit drivers. So if you are creating the DSN for use by Server, you should use that version. Confused yet?