Mon Nov 26, 2007 7:19 pm by Figz
Thats weird. I actually just backed mine up tonight. See if any of these steps differ from what you are doing.
1. Plug USB drive into the PS3
2. Go to your game saves and hit triangle
3. Select Copy
4. the drive should show up now and you select it.
5. wait for the save to be copied
If none of that works try browsing to PS3Brew.com on your ps3 browser and see if you can upload it straight from there.