Same here, also on 740G, but on other 2 machines with 780G
it also happens.
And adjtimex helped me on all 3 machines.
Running it in self-calibrate mode (that 70 sec thing)
plus running ntpd was enough for me for now.
What's interesting is that some time ago it worked just fine,
and, which is even more interesting, windows on this very
hardware shows quite good time stability (WITHOUT setting
the time using [s]ntp, its ntp client is disabled).
Well, sorta. Given the amount of hardware that exposes this
behavour, AND the fact that it worked fine with previous
kernels (I think it was ok with 2.6.26), AND that windows
works just fine, it's not "calibration of your system"
question anymore. It's now kernel bug question... ;)
BTW, the same Gigabyte GA-MA74GM-S2H mobo is here.
Other motherboards that exposes the same issue here:
M3A78-EM (Asus, AMD780G)
M3A-H/HDMI (Asus, AMD780G)
It never happened (so far) on M2N-SLI DELUXE (also Asus,
nVidia MCP55) and on M2N-VM DVI (nVidia MCP67).