@sagargv, I had experienced a similar problem sometime back.Here goes the story.
I had borrowed my friend's modem to check and confirm my Netgear modem is not the cause for my Dataone woes.All the network settings were configured correctly in the modem and I only had to change the user id and password in the modem to make it work on my line. I had the same broadband problems with this modem also - inconsistent speeds most of the time and even worse than than a dialup connection.After confirming that my modem was not at fault and it was a problem on the BSNL side, I put back my friend's user id and password in the modem , returned the modem to my friend , connected it to his computer and the problem surfaced. The modem will establish sync but no website will open and IE almost always froze. I was unable to even type 192.168.1.1 most of the time and when I did succeed it will not open.I was in a fix.
I reset the modem and put all the network settings in Windows except the User Id and password and tried. The same problem. I was still not able to open 192.168.1.1.
I was puzzled. I had no time to troubleshoot. I was sure that all the settings were right in Windows and the modem was configured correctly ( I brought back the modem to my computer and reconfigured the modem settings after the reset)
Cutting short any troubleshooting process, I restored his system using an image taken two months back, entered all the network settings in Windows ( he is still using Windows ME) and voila everything worked fine.I was able to access 192.168.1.1, IE was not freezing and was opening all the sites and I was relieved.
My friend confided he had experienced abysmal speeds and IE freezing many times before too and he never suspected any problem with his PC.It is all working fine now as never before in the immediate past.
And so what was the problem? I presume that his computer was inflicted by some malware which prevented the normal operation like opening 192.168.1.1 and other websites. It had nothing to do with the modem settings or network setting in Windows.
I always advise all my friends to back up their system when it is working good so that problems of this nature can be resolved in a jiffy instead of breaking one's head trying to troubleshoot and spend enormous time trying to seek the root cause and eliminating it.
Hope you get the moral of the story. Good luck.