Some of my keys don't work from time to time

Question

Now and again the 'h' and 'g' and backspace keys on my hp pavilion zv5000 laptop stop working. The problem is intermitent - sometimes it lasts for hours, other times a whole day or more. The keys will eventually start working again for no apparent reason. Restarting has no effect, neither does uninstalling and reinstalling the keyboard driver.