mouse movement problem

hi, i had logitech wireless MX3200 mouse on win7 32bit about a year ago on core2duo + 4GB RAM.
i had a problem, my mouse vertical movement sometimes stopped, could only be moved horizontally and only 1 way in vertical movement. sometimes it could only be moved up, sometimes could only be moved down, but horizontal movement was intact.

i thought it was the mouse, since i dropped it alot, or the receiver, since it was wireless. then i bought a razer lachesis. the problem still happened
i installed the latest firmware and driver, and updated all windows updates. still the same, but it got better when i turned the dpi to 4000 dpi (the highest the lachesis can support), sometimes the problem occured, but very rare.
the strange case was the mouse unbelievably fine when playing games (first person shooter etc), only on windows. so i thought it's the OS.

then a week ago i bought a new PC, now i have i5 + 8GB RAM, plus a professional version of 64bit win7.

for a week, i thought the problem was gone
but then, today i worked with extra multitasking and pushed my PC to its limit. the CPU usage and RAM usage was near 100%.
the problem came back sometimes it can't be scrolled vertically again.

then i remember with my core2duo, everything is almost 100% usage. so i think the vertical mouse movement problem has something to do with CPU usage.

please help. i multitask alot.

Probably too simple, but have you tried new mouse batteries?

my 2nd mouse is not wireless, it's wired razer lachesis :) i changed the mouse, the OS, the PC and still have the same problem. i think it's windows.

please help (