Where did you put the files? In G:\ ? If so then you may only place so many files there due to filesystem limits. If you made a subdirectory then that limit is removed.
Bob
I recently bought a 1gb PNY sd flash memory card. I use a GE 10 in 1 card reader.
I am trying to out 1 gig of music on the sd card, but it will only hold 545 mb. It's showing that I have over 400 mb remaining.
When I try to add more files it says..
"error copying file or folder"
"cannot create or replace "file name" "the directory or file cannot be created."
I know that some of the sd card disk space is needed for formatting etc, but 400MB seems excessive.

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic