I'm having trouble with my copy of Mount & Blade: Warband. The game barely seems to register the Tab key. When using the Tab key to exit a location, I have to hold it down for several seconds before it will register. Merely pressing the key will not work, nor will pressing the key repeatedly. I'm using a laptop with a USB keyboard attached and I've had this trouble with both the USB keyboard and with the laptop's built-in keyboard. What's wrong? Is anyone else having this problem, and how can I fix it?

It seems to be a bug that isn't fixed yet. It's sometimes working again after a restart.
As a workaround, try re-mapping Tab in the game's options to an unused standard letter key.