Sorry for replying very late.. but I saw in your screenshot the lack of DNS server's true address.. I'm also using BSNL's broadband in Fedora 12.. its working fine.. Just follow these steps.. I'm sure they will work :-
Step-1 - Right click on the network manager icon and click on edit connections
Step-2 - Then, edit your connection (eth0 to be precise)and manually enter these terms :-
IP - 192.168.1.2
Subnet - 255.255.255.0
Default Gateway - 192.168.1.1
Primary DNS Server: 218.248.255.194
Secondary DNS Server: 218.248.255.162
It may ask for your root password..
Then restart the interface or the computer and post what you experience.
---------- Post added at 03:54 AM ---------- Previous post was at 03:53 AM ----------
I'm 100% sure that the DNS address (192.168.1.1) which I see in your screenshot is the primary culprit of your problem.. Just replace either with these ones that I gave you.. or the one in your screenshot..