We had this problem with Turbo Tax too. I ended up filing married, but separate and I THINK (sorry, my forms are at home and I'm at work), that I printed them off and wrote 'FOREIGN' in for his SSN. If the system doesn't let you type that in (which I don't think it does), then just print it off and write it. You can't file electronically anyways, so you'll have to print off your forms and mail them in.
I tried to get him an ITIN and they denied it, so unless you're claiming your income as well, I wouldn't worry about it.
I'll double check my forms when I get home, but I'm certain I didn't have the number for him and the box said 'foreign'. I just can't remember if Turbo Tax accepted that or not.