Do a search for a file recovery tool for illustrator as there're a few about. So if you have a lot/few then it might br worth spending some money on it: http://www.illustrator.fixtoolbox.com/
When it happens to me and it does it is usually something like either a font problem or artifacts off the art board. I normally get it to read by using "Place" from the file menu. Also if it is not on your hard drive then please transfer it your drive and try Placing it from there. Hope that helps and welcome to Talk Graphics and I hope you post some more when you overcome your problem. Since you cant do PM's (private Messages) and if you want our help with this problem you might try using something like DropBox and post a link for 1 day which I could then remove from here once someone tries to sort out your problem.