Windows 7 64-bit, nvidia gtx 570
Broken: 2.49b, official 2.72b, 6c2ce7a
**Short description of error**
The backtick key ` is unresponsive in blender. I tried to use it to toggle all layers in the 3D viewport and found that it didn't work. I then found I couldn't type it into the user preferences to try and find the keyboard shortcut for it, nothing happens when I press the key. I also can't enter it in to the blender text editor. I don't have a problem typing this key into other applications, as I typed it as part of this bug report.
The keyboard is a standard usb logitech keyboard, I have no hotkey software installed and I was testing with factory blender settings. I also tested a Windows 8.1 64-bit machine and also found the shortcut didn't work, so I don't think it's the keyboard.
I also tried with the windows on-screen accessibility keyboard and it also couldn't trigger the shortcut.
**Exact steps for others to reproduce the error**
Based on a (as simple as possible) attached .blend file with minimum amount of steps
1. Open blender
2. Press ` while in the 3D viewport to toggle all layers on and off
3. No toggling occurs