Are you saying the individual folders show up empty on the computer, or on the Fuze display?
If it’s the computer, try changing the USB mode. Settings/System Settings/USB Mode. It should be either MTP or MSC, not Auto Detect. Your computer can only see one mode at a time.
Try formatting the card again in the unit itself–Settings/System Settings/Format–and put it in MSC–which makes it show up like any thumb drive. Then try just sending over one album as a test.
If it’s the Fuze display, were these exact same files showing up properly from the 8GB card? Because usually not showing up, but taking space, means the tags aren’t being read by the Fuze, but that doesn’t make sense if it could read them before.
You can also test the card itself with H2testw, a program to see if it’s a counterfeit or defective card:
Provide some more details. What kind of files? How exactly were you moving the files (via Windows Explorer, through Windows Media Player, etc.) Are there a lot of files under Artist/Unknown, or Album/Unknown? That would suggest tag problems.