error in insert 80070003

[crags]

Hi, I'm using a Samsung Galaxy Note 2, and am having problems:

1: transfering media onto my SD card and
2: reading the media that is already on the SD card.

1- When I transfer files from my computer to the device's SD card, about 50% of it doesn't transfer and I get the error in insert: 80070003 message in the transfer log. If I try to send the files again they simply won't transfer over. How do I fix this?

2- When I first got the phone I manually transferred about 20 gigs of music onto the SD card's "audio" folder. When I connect my device in Winamp (pc), the media that is in that folder does not show up. Is there a way to access it?

Thanks