  We analyze the temporal evolution of accretion onto rotating black holes
subject to large-scale magnetic torques. Wind torques alone drive a disk
towards collapse in a finite time $\sim t_{ff} E_k/E_B$, where $t_{ff}$ is the
initial free-fall time and $E_k/E_B$ is the ratio of kinetic-to-poloidal
magnetic energy. Additional spin-up torques from a rapidly rotating black hole
can arrest the disk's inflow. We associate short/long gamma-ray bursts with
hyperaccretion/suspended-accretion onto slowly/rapidly spinning black holes.
This model predicts afterglow emission from short bursts, and may be tested by
HETE-II.
