KeyboardPushed gets stuck

[theteapot]

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Partly solved - It's something to do with my computer, since another computer on my network can run it fine. It's not my code, so I've removed that.
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When I run the following code on my computer, and hold down some arrow keys to see what it does, it works for a while, but then it gets stuck on one direction - almost if ExamineKeyboard() has got stuck, and is returning the same result.

Now, I don't think it's my keyboard, since it works in Windows programs, and I don't think it's DirectX, as I've run other programs that can get the same result without getting stuck, so I don't know what's happening.