See if you can release the calipers in the same way you would do so when doing a brake job. Wedge a long screwdriver into the opening in the caliper so it lodges in the vents in the rotor. Dont press against either outside surface of the rotor (will damage surface). Then pull towards you to force piston back in and hopefully free up calipers..... however, you don't specify man/auto. If its a manual and you've had your e-brake on the whole time, I would agree with hockeyfan27 a good place to start would be the e-brake.
2009 335i Xdrive
Factory M-sport package
BMW Individual Audio
Pretty much every able factory upgrade by previous (1st) owner.
Performance upgrades thread startied