[beagleboard] PM on Beagle Board,

This is the problem in the core chip itself.
You can find the detail of this in the errata sheet of OMAP3530 at page
" Details: The USB TLL Save-And-Restore (SAR) + USBHOST TLL locks
up system during CORE_OFF and suspend to RAM. A hardware issue in the
TLL block causes a deadlock during the automatic hardware context saving
of the TLL block. On second hardware SAR, the save mechanism does not
function as expected; this is causes a lock-up in the SAR.This issue
impacts the OHCI TLL, PHY, and EHCI TLL modes. This does not impact HS
PHY mode.There is no workaround for EHCI mode (HS TLL).

Workaround(s) OHCI (FS TLL or FS PHY modes) : In OHCI mode, software
Context / Restore is functional and will be integrated as part of
mainline releases. This is a full workaroundfor the hardware issue."

There is no any workaround as I know. But the BB Xm rev C version will
have this thing fixed as said by experts.

However to save power you can decrease the power as less as to .35Watt
(w/o any usb peripherals) without going down to suspend mode.