Subject says it all, I guess the way it probably occurs is:
1. Delete file from USB drive (not sure if precence of recycle dir enough)...
2. Wait a bit
3. Run handle.exe (sysinternals) and you will see:
[code]C:\> handle y:
Copyright (C) 1997-2006 Mark Russinovich
Sysinternals - www.sysinternals.com
ObjectDock.exe pid: 3888 1C0: Y:\RECYCLER[/code]
4. USB drives Eject should now fail.