The Canon Japan website has officially announced the availability of Firmware Version 2.1.2 for the Canon EOS 5D Mark II
The press release says that it provides increased reliability of communication with UDMA7 CF cards which will be released after February 2012.
To upgrade your Canon EOS 5D Mark II to Firmware Revision 2.1.2 you must already be on revision 2.1.1
The Canon EOS 5D Mark II Firmware Rev 2.1.2 can be downloaded from here:
Update you can download these firmwares from the Canon US site (in English rather than the above Canon Japan website) at the below URL:
The official canon press release can be found here: