Wireless keyboard - strange behaviour

[Tefler]

We have a Microsoft USB Dual Receiver Wireless Keyboard. It's been a great thing to have - easily repositioned to suit different users and with useful hotkeys. However, yesterday it started behaving strangely. At first, it was missing out some of the letters typed. It didn't want to put exclamation marks or the number 2, for example. Gradually, the problem got worse: every third or fourth keystroke needed to be made five or six times before anything appeared on the screen. It wasn't one of those 'delayed reaction' incidents you get when the computer's trying to do something else in the background, it just didn't happen. Then, the 'sleep' hotkey refused to work at all.
I turned the machine off completely overnight. This morning, the characters appearing on the screen bore no relation to the keys pressed on the keyboard and were, in fact, completely random. We put the machine to sleep, woke it up again and suddenly we were back to normal.
The only thing that happened before the problem was an upgrade of Firefox.
If anybody has any thoughts on what may have happened here, I'd be grateful for a hint, just in case it happens again.

[Tefler]

Oh Zacsmaster - it seems so simple, doesn't it? I did check the battery signal on the computer, which suggested there was no problem. However, I've just changed them and, at present, you see to have achieved a cure. Many thanks!

[Tefler]

Oh dear - I spoke too soon. This seems to be an intermittent fault (the worst kind!). Now it's working fine. 5 minutes ago, it was bag to the weird ways again - in spite of the new batteries.

[spotit3]

Same happened to me recently. I rang Dell as it was still under warranty and they were very helpful. Eventuaaly took over by remote control and I think they changed a driver. Works fine since then.

[Tefler]

Thanks for the hint, Spotit. I've installed a new driver, so we'll see how that works!