Cheap card?

I have a couple "cheap" cards with slow write speeds (Class 2), and if I use them in video mode or 3-shot burst, I tend to have a couple bad files in the mix. No-where near as bad as you describe, but using a Class 4, I've never had a problem.

I tend to rotate my memory cards instead of pulling the camera down, and this is what I noticed when I used older, cheap memory cards.

I also have a Bushnell Trophy Camera, but it's ~3-4 years old.

Edit - Normally the "class" is in a circle on the card. 2,4,6,8