Wireless N/W connected but browser not connecting

[guhanath]

Hi,
I recently purchased a brand new Sony Vaio FW series notebook..(in USA)
It has Vista Home premium(64 bit), Windows Live one care trial..
I configured my internet in the laptop.I was able to register my product,update live one care and the wireless network says it is connected..

I started IE it worked fine for few pages then it says page cannot be displayed.
I tried to diagnise the connection but windows says it is already connected and no errors.
I pinged some websites in command prompt and they replied back.
I installed firefox to see to see if this is a problem with IE, but firefox too behaved in the same manner.
I tried to update adobe reader and it downloaded the updates.
After some idle time it worked again for few pages and then got disconnected but ping worked and wireless network is still connected
The firewall is configured to allow both IE and firefox to connect..the web.
So confusing to understand the behavior, I have another notebook which shares the same wireless n/w and it worked fine
without any issues. The internet connection settings are right.
When I restart the machine it connects for few min and then disconnects
what could be the problem and how can I fix this?