I have known circumstances in which the Recycle Bin folder seems to acquire files which resist all efforts to remove them. In one case, the only way I could resolve the problem was to boot the system from a CD-based Linux distribution, and delete the whole Recycled folder. That's only a little bit better than formatting the drive and starting again. Let's hope we don't have to go there ...
After the erase, does anything show up when you open the Recycled folder; in other words, does Windows think that the Recycle Bin is empty? If it does, can you put some sort of test file in it, and empty it again? If that works, what happens when you put another test file in it, and try to erase the contents of the bin?
If your files are showing up in the bin, can you restore them? If you can, can you erase them directly? If not, what condition are they in; in particular do they have a length, or is the length 0? If the length is 0, the data at least will have been overwritten, and you could just try deleting them, so that the MFT entry is overwritten next time you run a free space erase.
Another option I sometimes use with recalcitrant files is to use the (free) recovery utility Recuva, which has an option to overwrite files it finds. This saves doing a complete free space erase just to remove traces of a couple of files.
David
P.S. At the risk of sounding fussy, when you exited Eraser before re-running as Administrator, you did close the running process from the System Tray, didn't you?