Nokia :: 5800 Temporarily Loses Wlan

I've tried lots of things and still no joy. Basically, my 5800 (with v50.0 firmware) keeps losing my wlan - even when sat physically next to it. It doesn't lose connection (since it's not connected), it loses (apparently loses) the wlan signal but immediately finds it again - all whilst I am sat watching it within the connectivity->wlan page.I have sat there, with my laptop running a signal analyser, poling every 500ms and the router's signal doesn't drop at all, yet my phone is sat next to it and every so often it'll show my wlan go from "known" to "unknown" and the signal goes from 100% to none. 8/10 my phone will connect to my wlan for internet use or downloading emails, 2/10 it'll resort to contract WAP since it believes my wlan is unavailable. My wlan broadcasts on a channel that is not overlapped by my neighbours, and my laptop shows a constant 100% signal strength, regardless of other wlans that may or may not be broadcasting (those wlans that do occasionally appear are very weak, and the 5800's dropping doesn't appear to coincide with their temporary appearance).

The wlan is running in 802.11g mode, and is WPA protected. I have tried having no security on it, same problem. I have tried adding the MAC address to the router, same problem. My wife has the same phone, same firmware, and hers does the same thing - except at different times (it's not like the both drop sight of the wlan at the same time).It appears, though I can't be sure, that if I go in through the connectivity->wlan page and choose my wlan and "connect" to it, then it stays connected and never drops. Unfortunately, this isn't an acceptable work-around since I have configured my phone to periodically check for emails and I don't want to have to remember every time I come home to manually connect, etc.Can anyone please suggest a course of action or investigation for me to undertake, since this is really, REALLY starting to confuse me!