When downloading content from the Store to a PSP with an 8 GB or 16 GB Memory Stick Duo media inserted, you may see a message indicating that the media does not have enough free space, even when sufficient space exists. Update 5.01 resolves this issue and will be coming soon.
As you can see it’s an issue, but who really has that kind of a Memory Stick? If you do, you’re pretty expensive there.
PSP (PlayStation Portable) v5.01 Update [PS BLOG]