A CRC error basically means there was a write error. The CRC is used to make sure the write happened correctly.

It is sounding to me like either the card has issues or the 800.

Assuming the card works fine in other devices it sounds like the 800 is the issue. I just can't say for sure since some smaller cards work fine in the 800. Having another larger card to try could tell a lot. I have used 2, 4, and 8 gig cards in my 800 without issue so I know in general the 800 can handle them.

Sorry I can't be of more help. I am not sure where to go from here.