Hopefully you've already tried this but JIC-
fire up the unix abyss that is the Terminal and type:
chdir (make sure you typed a space after that then drag the folder into the terminal window)
hit return
type ls (this will list all files in the directory you just selected) PS thats an LS, just lowercase.
if the directory is empty, then you have a bad block or B-tree or something equally dark and scary, if not, use:
sudo rm file-name-goes-here
type in your password (the characters WILL NOT show up, just keep typing)
return
repeat ls and sudo rm until directory is empty, then sudo rmdir (ReMove DIRectory)
Hope this helps!
Cheers,
theDan