Overheating and 'cannot access card' regularly when recording video

[Martin]

My canon 7D is regularly over-heating. I use a battery pack and
generally 30mb per sec cards. A lot of my projects I am shooting 4-
minute clips, with around 2 minute down-time inbetween. After 40 mins
or so, it overheats and turns itself off. I lose the last recorded
file. I can turn the camera back on after about 20 seconds but lose
the performance/interview etc last recorded. It's fairly common with
the 7D but a few people have suggested that when they use a monitor it
doesn't over-heat. Does anyone know a way of turning off the LCD
screen without having an external monitor?

Occasionally I get a message saying 'Err 02, cannot access card,
format or re-insert'. This also causes me to lose the last file. Any
advice on hwo to avoid this?