Vista - Why MS Wireless Laser Mouse 5000 does not work OK?

Hi

My MS Wireless Laser Mouse 5000 (part of the combo with 5000 kbd) is not
working OK, specifically the wheel functionality, under Vista Ultimate
64-bit full. Previous MS Laser Mouse 6000 wired worked great, but now I have
these problems:

- Google Earth zoomed in and out turning mouse's wheel, now it zooms in
only; and
- Inside a Virtual PC 2007 session, one have to turn the wheel several times
to scroll a few lines.

Now I tried the first DX10 game that's shown up (Lost Planet DX 10) and the
mouse pointer is unusable to select menu items.

Any ideas? I have applied all updates to nVidia Forceware, to no avail
(8800GTS).

Thanks

Edric