CnC Pro and constant contour

I have trouble using the Constant Contour feature in CnCPro.
I run a lot of step and repeat files .ie:
G00x20 Y20[in G90]
g22 P1[subroutine is in relative,and I turn constant contour on and
off inside subroutine]

all is well until next G90/G00 move to next location,then machine
"gets lost". Not from stalled motors but I think from my computer
[P266} not keeping up.
In the bios there is a setting under chipset features "gatedclock"
if the above is set to enabled could this be problem? Will I gain any
cpu performance by "disable" gated clock?
OR,, is the 266 just not fast enough to keep up with constant
contour?

many thanks
Carl