Comment 16 for bug 7560

Confirmed in gutsy.
My recommended fix is that when you choose to empty the trash, nautilus should do either this:
if [ `rm -fr ~/.Trash/*` != "" ]
then
chmod +w ~/.Trash/
if [ `rm -fr ~/.Trash/*` != "" ]
then
#Do the "This file could not be deleted" thing
fi
fi

Or:
chmod +w ~/.Trash/
if [ `rm -fr ~/.Trash/*` != "" ]
then
#Do the "This file could not be deleted" thing
fi

The former would be faster if most files are writable (probably the case), but the latter would be would be faster if most of the files are not writable.