I can't tell if this is some USB or PS2 keyboard so unplug and plug back in. For the USB keyboard try another USB port that Dell tells you supports the keyboard.
Dell B130 Desktop purchased new 7 years ago. Operating System is Ubuntu 10.04-4 fully up to date.
My keyboard started acting nonresponsive 1st the 'd' then a few weeks later the 'a' for a few days, now no response from any key.
What is my most likely problem?
I have been very satisfied and have had no prior issues with the machine.