Lindsay Lohan's relationship with Avi Snow lasted only slightly longer than her most recent stint in jail -- seems the rehab-bound actress and City of the Sun guitarist are already kaput.

Barely a week after the two were spotted canoodling at a COTS show, insiders tell E! the brief romance is over.

No one's quite sure why she and Avi called it quits, but maybe it's because her upcoming schedule is pretty packed -- she's booked on Letterman next week, and then she's planning on hitting Coachella in Southern Cali. ('Scary Movie 5,' in which she cameos with Charlie Sheen, premieres next Friday, but supposedly she's skipping the event.)

More recently, Lohan spent last week in Brazil earning some coin (and hanging out under tables), and was having such a good time that she even extended her stay.

And then, of course, there's the little matter of her upcoming 90-day rehab in a lockdown facility that may or may not exist.