HAVE WIFI ICON BUT NO NETWORKS SHOWING?

Hello People

I have searched these forums but can't seem to find this particular problem;

I boot up in Vista and everything is fine for 30 minutes or so then suddenly my WIFI connection will drop. I will then hover over the icon and it will show I'm still connected to my network but I'm obviously not. I then right click and choose available networks and there won't be any showing. After trying all sorts of possibilities the only way I can get my connection back is by rebooting.

I mentioned Vista because this problem only occurs when I use that O/S, if I boot up in XP, all is well and the laptop has no problems whatsoever, it NEVER drops the WIFI connection.

It's an Aspire 5633WLMI with an Intel PRO/Wireless 3945ABG with driver version 12.2.0.11 dated 17/11/2008.

Any advice would be greatly appreciated.

John