MSWord loses focus

When typing using MSWord 2K, and I leave the PC for more than 5 or 10 seconds, the cursor stops blinking and the title bar dims to grey. When I return and move my mouse to return the focus to the page, often nothing happens.

If I do not notice that the focus is lost and continue typing, I can be halfway through my typing before I realise that the cursor is back where it was when I satarted.

Any ideas? Some of my freinds have experienced the same problem, so it is becoming a problem