Yes. Whenever I try to copy files over USB like that, the tablet locks up and reboots after copying about 10MB.

I've formatted the card (both on the tablet and on the computer). I checked things out with fsck too but it just fixed some issues that appeared related to incomplete writes, probably from the copies that never finished. Fixed those issues and trying to copy another file caused the tablet to crash.

I also got a hold of a SDHC card reader. Curiously it seems the video I recorded with the digital camera was corrupt and unplayable, but I had no problems copying some large (hundreds of MB) files to the card with no apparent corruption. (I tried a large .zip file and a large .wav file, both seemed fine.)