One laptop has Netgear connectivity RF issues DG834 G

[#1]

Any clues as to this annoyance valued 
3 Laptops, 2 on Vista, one XP Pro.
Only one (Vista machine) has internet problem; it sees router OK and is connected but I have the ! exclamation mark showing against connection.
Done normal IP Release/Renew commands, no change.
Asked Windows to sort, no change
Reset router; no change; 2 are OK, 1 not.
Hard wiring for a mo, it gains internet connection, but when
I remove, back comes the ! mark 
Deleted connection profile on problem Dell laptop, raised it again,
but the triangle persists.
Any other tasks I should be trying.?
Thanks

[#2]

Has the laptop got an on/off switch for the wireless? If it's switched off in hardware, Windows doesn't always recognise that, and shows all the usual configuration and connection options, but it just doesn't work.
It'll either be a physical switch on the laptop itself, or a key combination.

[#3]

Yes the Dell has an off slide switch; tried that (ie on /off/ on) in hope it would refresh things.
Alas no

[#4]

Gel, its been a while since I played with Vista (on XP at the mo) but what information do you get if you hover over the network exclamation icon?
Did you get asked what type of network it was that you were connecting to? if I remember right you can tell it that you are on a home network or a public network? if you don't tell it it blocks the connection.
Edit:
ALSO the basics: you have checked the network key is correct and that the network card / drivers are compatible with the security settings on the router? Older hardware might not work with WPA2

[#5]

Thanks.
Here are some screenshots; one with the problem is the Dell, and snap shows wired connection OK, but problems on the wireless.
On another Medion I have, also running Vista, wireless is OK, though strangely
shows "Wantage" a previous SSID and the current.
One other oddity I noticed that even when wired the Dell has an issue with one
ISP when running Magic Mail prog; it polls several ISP's I use,
and shows me what's waiting.
Other laptops have installed too; 2 that are OK wirelessly, have no problem with checking
all the ISP's listed, on the Dell it can't connect to my one tel ISP:
that may be unrelated, but is certainly odd.
Settings for that programme are identical for each.
Dell using AVAST AV s/ware, others using AVG Free on one, McAfee Corporate on my other Dell.

[#6]

Update
Well when I next booted up problem child I had wireless connectivity in full; no changes
made to laptop or Netgear; go figure.
On the other problem with Magic Mail/Thunderbird not being able to poll Onetel ISP, by turning
off Avast, the ISP connect works; never heard of an A/V prog affecting just one ISP; have others?
I know many say having your A/V prog to check e mail is waste of time anyway