I’ve had a similar problem that I’ve suspected to be heat as well.
I’m using a Hoodman Raw adapter with Delkin Class 6 SDHC 16gig cards. I’m also using a Swit90 battery. After shooting for a full 3 hours of hand-held in 1080HQ 24p. Usually it’s towards the end of a full card I’ll get a ‘media restore’ error. If i shut the camera off, switch the adapter to a different slot, restore the media and keep recording, it solves the problem, even on the same card. But sure enough even if i switch cards and switch slots after the error, if my camera is hot enough, I’ll get another media restore error. I strongly suspect the heat is an issue. When I pull the adapter out of the camera it’s really hot to the touch.
Any ideas or suggestions would be most helpful. For now I’ll try to switch slots between cards to give one a rest, or perhaps shoot with the door open?
Thanks,
Ashley