Thanks to Mom, I found out late yesterday night that while the modem was on, both the lines were functioning. Pulled the other line out & things are back to normal. I guess I need to get the modem checked. Sure feels nice to have the old connection speed back.
PS : After a few calls to BSNL (this was about 2 days back) the lady could track down the problem as "somewhere between the modem & my comp". Will call her & tell her about this tomorrow.
PPS : A huge thanks to louiswu for the Pudhiya Mugam mp3 collection. Amazing songs.