No - you cannot kill them, period. kill -9 does not work either. And it is not kernel bug, it is by design. All signals are blocked until those processes leave the D state. They either leave the D state or the system gets rebooted. No, rebooting does not have any problem with these guys.
The usual culprits for this kind of problem are removable media devices like a cdrom. The device may be defective or somebody found a way to do something stupid.
