Dell Laptop Vista - Connected but No Internet

Hello,

I have a wireless network, 1 desktop (W XP), 1 laptop (W XP) and another laptop (Vista) and Trend Security running on all 3.

My desktop & XP laptop connect to the wireless network and internet absolutely fab, however I am "connected to network", but am unable to get any wepages open, they "hang" for a lifetime! - I use Firefox as my default browser. After selecting my "diagnose" I am informed that it is due to "key ports" ("failed to connect to the service. This could be due to an improper proxy or firewall settings. Pls review firewall setting. Proxy settings can be accessed through Windows Live Messenger Options". .................blah blah blah) I have switched both Windows & Trend firewall settings off, but still no internet. Email is sent & received perfectly.

I think the laptop came with a free period of Norton, but I changed to Trend as I had a 3rd licence available for use. After reading other threads perhaps I have some "trails" of this left behind which I need to obliterate.

This problem has occurred only within the last week, but prior to this I had been having router probs (this was resolved with the help of a very nice man at Linksys support) and all was working well after that for at least 3 days.

This is my daughter's laptop so I am not aware of any "version updates" that have been agreed to - I do request that she does not accept any request of that nature without running by me 1st (not that I am a PC whizz, but just so I can relay any info that maybe relevant in circumstances like this!

Please can anyone advise how I get my Internet back on my Vista operated laptop?
Cheers