ACPI C-state and power management issues on Latitude XT

I'm running linux on Latitude XT (I know these series aren't officially supported by Dell) with 1.2GHz C2D, but without disabling some power management features, the system is really unstable. Without disabling C-states deeper than C1 (processor.max_cstate=1 kernel command line parameter), system randomly freezes, 'powertop' tool reports bogus values (like 8000 wakeups/sec) and the system is not able to even fluently play video. BIOS is updated to version A05.

Also, when bluetooth (Dell Wireless 350 Bluetooth) is enabled, it generates 200 interrupts per second, which is too high value for device, which should just be idle, as I'm not doing any bluetooth transfers.