Intermittently, my keyboard will stop working when holding left Shift and typing t,y,g, or h. Typing any other key with left Shift will work just fine. This is happening on Windows 7 on a Lenovo 420 laptop.

The problematic keyboard is an IBM type M keyboard connected to a Trendnet KVM. The laptop's built-in keyboard works fine.

  • does the keyboard work fine in another computer without a KVM?
    – nc4pk
    May 19, 2012 at 17:41
  • No, I have connected it to the laptop without the KVM and the problem persists.
    – fdediego
    May 26, 2012 at 19:02
  • I've experienced this issue on my keyboard as well. It occurs with both left and right shift, and also affects [, ], and '. It's specifically an issue with the keyboard, as I've had it happen with the same keyboard on two different PCs.
    – Stevoisiak
    Mar 26, 2017 at 1:01

1 Answer 1


If the keyboard has the same issue with other computers, not connected through a KVM, then this really sounds like to me that there is some sort of conductive material getting in the way periodically, like a small drop of water or something of the sort, within the keyboard.

If it works correctly, then it could be a problem with the KVM forwarding the keyboard signals.

Because we are using 2 different components here which could be the source of the fault, I would recommend attempting to isolate which component is failing by eliminating one of the variables. Either replace the keyboard or the KVM and and go about your work as usual to see if the failure ever happens again.

  • I have connected it to the laptop without the KVM and the problem persists. Now it happens always. I don't understand why they work alone and with "right-shift", but they don't work with "left-shift"
    – fdediego
    May 26, 2012 at 19:06
  • The problem is in the keyboard. With another one the same laptop works fine.
    – fdediego
    May 26, 2012 at 21:49

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