My MTNL connection has gone mad all of a sudden,
In Bridge mode, its unable to open any sites but downloads are going quite strong.
In pppoe mode, browsing is ok but download speed is pretty sluggish.
It is the problem of DNS server. DNS setting is not configured on your system I suppose.
Goto your Internet connection>Properties>Networking tab>Internet Protocol(TCP/IP) Properties and enter the following DNS servers
Preffered DNS server:-208.67.222.222
Alternate DNS server:-208.67.220.220
These are the OpenDNS servers. I hope it will help you.