Cannot ping DIR635 Router gateway so no web

[xtopher]

I know many posts on many forums have tried to solve this topic but usually the solution is not abc etc or just peters out. But I need to try as I have been on this for 2 weeks.
I have a new quad core PC running Vista Premium and SP1
Am connected to a D-Link DIR635 router and to a Virgin cable modem
Have managed to set up the router to make wired and wireless connections successfully. My PC is in an upstairs room and there is excellent wireless signal strength. Here's the scenario:
PC when wired direct to the cable modem - no problem getting web pages
PC when wired to the router (now inserted between PC and modem) - no problem with getting web pages
Toshiba Laptop running Vista Premium finds the wireless connection getting web pages no problem operating anywhere in the house
PC connected wirelessly can only receive the odd home page eg Virgin, Yahoo
Note when wired I can ping the WAN and LAN IP addresses no problem
and when wireless the same IP's return 100% lost pings.
Logic tells me then that most of my hardware is working in particular the router and modem boxes. The only item that is NOT common to the above scenario is my PC's internal wireless adapter although my pc tells me it is operating correctly. I am totally new to wireless/networking and have learnt a lot from very nice people on many forums but it does seem to be a large problem area with very few posted solutions. I have looked at many parameters on the routers web based setup and on my PC's various properties and cannot find anything obvious. I am now stumped and out of ideas. Yes it's been rebooted countless times. Something tells me it has to be a simple command or a conflict. I am sure as soon as I am able to ping the wireless router gateway all will be solved! Today is Mon - will be away from this infernal machine until Thurs eve! Any ideas most welcome b4 I make an expensive support fonecall.