basket case - what wireless router do you have? Does it reliably support Power Save Mode (PSM)? Are you running the latest firmware on your router?

PSM allows the N800 to shut off the WiFi radio several times a second in order to save battery power but it can only do this reliably if the wireless router (access point) also supports PSM - if not, the N800 will have trouble communicating with the router. By default, PSM is enabled on the N800.

If your router doesn't support PSM (or supports it badly) access the Connectivity Settings dialog in Control Panel on your N800 and Edit your WiFi connection then go to the last page and click "Advanced". Select the last tab ("Other") where you can change "Power Saving" to Intermediate (saves less battery) or if absolutely necessary to Off (saves no battery power). With it set to Intermediate or Off your battery won't last as long but at least your WiFi connection may stabilise.