QNX6 and Power Mgmt = Lockup

I upgraded a QNX4.25 machine to QNX6 - and found that after about 14 minutes
of no activity, the machine would totally lock up; no response to console
keyboard, mouse, network etc. When I disabled the Power Management in the
bios the problem disappeared. Behaviour is similar for QNX6.1.0. QNX4.25 did
not seem to be sensitive to this. Is there some way to de-sensitize QNX6?