[Windows] Cubase ignore Control button

cubase has so many bugs,
this is one of them that so bother me.

I’m using win7 64bit with C7.5 64bit (but this bug happen on C7 too),
sometime when the project get a bit heavy,
and then I do hotkey on my keyboard like control+s or control+z (or any hotkey with control button),
Cubase will ignore(or miss catch) the control button,
so “control +s” will becomes “s”,and “control + z” becomes “z”,
this will made maybe some accidentally solo track or accidentally not saving the project,
please fix this.
thanks!