copying to SD card returns "disk full" error [but it's not full!]

so i just got this Samsung digital photo frame...

I also got a 2GB SD card from Verbatim, so i can put it in the frame and display more photos

The SD card came with a USB reader.

I grabbed about 300 JPGs @ approx 300k each (approx 85MB total), and the copy operation choked at about 13MB. I got a "-34" error (disk is full), but it's obviously nowhere close to being full

now here's the interesting part...

when i insert the SD card into the +frame device+, and connect the FRAME via USB, two new drives mount:
1) the frame's internal memory
2) the SD card

When I try to copy the SAME photos to the same SD card "directly" via USB, the copy chokes at the same point!

I also tried skipping the file where the copy fails, but the one AFTER it fails, as does the one after that, etc

I've also taken the same SD card + reader, plugged it into my PC, and successfully copied approx 1GB of data (albeit different data)

Finally, I've tried formatting the card in Disk Utility, to no avail

So in summary:
1) cannot copy all files via USB card reader
2) cannot copy all files when SD card is read as a drive when inserted into frame
3) disk format did not help
4) can copy 1GB of data when card/reader is attached to PC/Windows

Is it the card?

Is it the reader?

Does anyone have suggestions for cards &/or readers that they can verify as Mac-compatible out of the box?

thanks in advance