i agree about the brand and USB connection use. those seem to be the strongest indicators thus far. I know for sure that the A-Data cards that i bought we not top-of-the-line cards at about $50 USD each off newegg.com. i have connected my n800 to a linux machine via usb for file transfers, to and fro, so i cannot say which is the culprit, if either could be.

i do have one of the A-Data 8GB cards in the internal slot which is working properly, and 2 SanDisk 4GB SDHC cards that have never been put in the n800, and i may keep it that way.

if kingston has a lifetime guarantee, i may buy that brand. does kingston have plans for higher capacities like 16 or 32 GB cards? Do other manufacturers have lifetime guarantees and cards bigger than 8GB?