OK guys, I was faced with this problem some years ago, so here's my answer.
Hopefully you own Acrobat in some form (not just the Reader, but the full version). This will mean you have the Acrobat Distiller. Set the option on Distiller to Press Ready to make sure your EPS retains all of it's press ready/CMYK information. Then drag your EPS into Distiller, the EPS will be converted into a PDF file. Now take this PDF and open it in Illustrator, you should now have no problem opening this new PDF file, just save the PDF you have opened as an EPS. I'd suggest keeping the original you couldn't open and giving the new EPS file a prefix to let you know this is the new one you have created.