From memory i think it is a motherboard fault. Ring Dell support and get them to replace the board.

Hi, I would replace the keyboard, 5 screws and it will fix the problem 99% of the time. The part No. is 3C048 for the US version, but check this. An alternative is disconnect the cable to pointer-stick. It is the narrow cable. If you choose to cut it, be sure to insulate the ends so they cant touch the internals.   Good luck with it.

We have had this problem with several of our 600s and 610s and have had the whole keyboard, touchpad and wrist-rest panel replaced by Dell under warranty. Speaking the engineers it seems that they do quite a lot these swops so it looks like it is a design flaw that appears after about 2-3 years.

When you log a support call you are normally asked to updated the BIOS to the latest version, also the touchpad drivers, neither of which has made a difference for the 5 I have personally dealt with but it's worth doing so to to save time.

 

Tim