From a press release from Canon issued today:
the hotly anticipated firmware update for the EOS 5D Mark II Digital SLR Camera is now available.
This new firmware will accommodate a great number of user requests for manual exposure control in the EOS 5D Mark II video mode. Manual exposure control while shooting video on the EOS 5D Mark II is expected to make a big impact with cinematographers and videographers using the 5D Mark II for high-end HD video production.
Please follow the link below to the EOS 5D Mark II product page on the Canon U.S.A. Web site to download the new firmware. Let us know if you have any questions, thank you.
http://wwwusa.canon.com/consumer/controller?act=ModelInfoAct&fcategoryid=139&modelid=17662#ModelDetailAct