I am posting this solution so people out there can search and find it. It's a network problem not easy to diagnose. You can find pieces of the solution out there. I am summarizing them all here.
So, I was doing family "IT support" again.
One of my relatives was having a strange wireless connectivity problem with her cable network. When connected with the wireless network, she could only browse google but nothing else.
The ISP is Comcast. The coax cable goes direct to the back of a Comcast issued Netgear CG814WG gateway / modem router, which provides the wired and wireless network. No problem with wire network, just wireless.
It took me a while through the process of elimination and solution searching from the net to finally figured out the cause and fixed it. At first I thought may be just the firewall security software (Norton) in her Vista laptop blocking access. Then I thought may be the wireless mini card in her laptop was faulty. But then I tried another PC (WinXP, different firewall software and wireless adapter), the same problem occurred. So the problem was not on the computer side, it's from the router.
Cheap and outdated router! The CG814WG may look like a normal Netgear router with it silver exterior. But its firmware is a customized Comcast firmware. The firmware provides not a whole lot of features. The wireless was set to WPA security. Turned out that was the culprit of the whole problem. While the router is ok with WEP, there's limitations when using WPA.
My hypothesis is that when WPA is enable in the router, some how it has a limitation on MTU size. Her PC was having a MTU of 1500. When requesting a page from a website, the PC and the website negotiate for an appropriate MTU. Most website will just send packets with MTU 1500, which when goes through the router, it fragments the packets and lost connection to the website. Only a few websites, such as google, set their MTU to lower than 1500, so their packets goes through the router successfully.
Reset the MTU in the PC to lower than 1500. I did the following in her Vista PC, which should work for Win7 as well.
1. Bring up the command prompt (cmd.exe) in administrative mode.
2. Type this "netsh interface ipv4 show subinterfaces" to show all your network interfaces. Take note on the subinterface number of your wireless adapter.
3. Type this "netsh interface ipv4 set subinterface interface=? mtu=1492 store=persistent", where ? is your wireless subinterface number.
For WinXP and below, you have to muck around in the registry to change MTU. Or just download Dr. TCP to do it ( http://www.dslreports.com/drtcp
Call up the cable tech support is not a solution, they are unlike to admit its their router's problem. In fact, my relative did, and they blame her computer! Don't waste your time. Use the solution above or you can use the work-arounds below.
1. You can use WEP instead of WPA, but you're sacrificing security.
2. Call up the cable ISP and ask to substitute their modem router with only a cable modem (no router). Then to go buy a better wireless router of your choice.
Hope this helps!