Imac having odd problem. Entering password at bootup, the computer does not respond to keystroke (usb keyboard), until it's been tapped multiple (but not consistent) number of times, then it will spit out several iterations of the same letter (but not as many as taps). Very difficult to backspace to correct. When that frustrating process finally gets a password, the computer works fine. After some use (a day or so) the keyboard starts not responding in a similar fashion. Rebooting is necessary.
We swapped out keyboards, disconnected any bluetooth devices that had at one time been connected. Run techtools and disk utility, no issues appear. Any clues/suggestions?