Keyboard lag can be caused by both hardware and software issues. Are any running processes eating up CPU cycles, or do you notice a lot of HD activity when this happens?
I had a similar issue with my ACER One Netbook, though with the trackpad and not the keyboard. Swore that it was a defective trackpad, as response time was lagging and at times would not not respond accurately. Was worse when recovering from sleep mode, requiring a reboot.
Turns out, I discovered it was the WIN 7 Synaptic driver for the trackpad which allows the use of gestures similar to a tablet. Uninstalled it, and instead used Microsoft's generic mouse driver. The trackpad now operates normally.