You could try talking to the finance, student accounts, or graduate dean office (or maybe all of them) at your university to see if they will work with you on this and delay having to pay tuition. I guess there may be a deadline for differing that could be a problem too. I wonder if they could let you hold off registering for classes since usually you can change them until the add/drop deadline, or wave late tuition fees. You may need your advisor or department head to help with this if the other offices say no.
I'm a current fellow and I've registered for classes but my tuition payment is now late because I haven't gotten my fellowship renewal for this year. So I informed the finance office about the situation and at the moment they have given me a one month late fee waver. Hopefully they'll wave it longer if need be. But at least they know I'm not paying for the moment, and I can drop the classes later if the renewal doesn't come though.
I don't know how accommodating they will be, but may be worth a shot.
