Still WRT54G probs

To recap, got Winbook laptop 1st floor, desktop and WRT54G on 3rd
floor. Works OK mostly...better since SSID changed, in case local
similar router(s) were interfering on same default SSID.

Over a day, or sometimes in short time, Speed varies from 5.5 Mb to
50+ Mb, and Signal Strength varies from Very Low to Very Good.
Slow/Fast does not necessarily correlate with Low/Good...I can get
slow/good or fast/low.

And it drops, or comes on unconnected, at various and unpredictable
times, tho it seems to happen most often, say, 5-7 PM. A techie once
told me that was due to closing businesses turning on alarms, but
this is a residential neighborhood...there are a few oold small stores
2-3 blocks away, not much else.

I don't know to blame the router or the laptop wireless card/software
or the relative location/antenna orientation/whatever.

I wouldn't normally suspect the laptop, but: an hour ago I restarted
the laptop, which had been connected before that, and it came on with
no connection. Restarted twice more - same result. Bur right-click the
TV icon in system tray -> View Available Networks showed window titled
Wireless Network Connection, with a little bar graph at top right
saying (when you point at it) "Signal Strength:Very Good...when it
won't even connect!! Could it be the computer, not router or other
reason?

I don't know where to go, and gotta do it this summer, as laptop and
router are under warrenty til early Sept. Ideas? Thanks,

-Brad