I've noticed that Windows (never had this issue with *nix) systems often steadfastly refuse to unmount removable media. Usually I unmount the drive, but when that happens I remove the drive without unmounting. I think some application blocks unmounting, probably explorer. I'll have to see if crashing explorer.exe first lets me unmount next time.
They're maemo and MeeGo... "Meamo!" sounds like what Zorro would say to catherine zeta jones... after she slaps him for looking at her dirtily...