Are you referring to the original jpgs or the new TIFF files? Have you tried opening them up outside of Elements? If you use explorer to open them up, do they error out or open fine? Download this free viewer (it should be your default viewer in my opinion anyway... it's free, lightweight and quick: www.irfanview.com) and try to open the files and see if they view in irfanview.

If they open fine via explorer/irfanview... then I would say don't use elements to do this conversion. You can use irfanview to batch convert them so give that a try.

Let us know if this helps...