A quick search of the web suggest that keyboard lag isn't uncommon on the G73, most looking to be down to iffy keyboard drivers, touchpad drivers or faulty keyboards.
I would start by having a look in device manager, seeing if there are any conflicts, & checking if there are any updated drivers available for the keyboard or touchpad.
If you don't have any luck there, I would take a note of the version of the ATI drivers & see if anything newer is available - if it isn't I would still try reinstalling the latest ATI drivers. if that doesn't work it may be worth installing an older version of the ATI drivers than you currently have, you may have to try a few older versions if you can get hold of them.
It may be that the currently installed drivers (which are most likely required for res adjustment) are conflicting with other drivers & that this may have happened a while ago when you (or the G73) did an ATI driver update.