Frequent Disconnections

Airtel TalkN'Surf 256 + NightULTopUp
Hi Guys, Recently I took the initiative to "optimize" my Internet Conncetion. Earlier I was getting a constant 25-30Kbps any time of the day. After going thru various threads on this forum I found that my router uses MTU value of 1500 which is not optimized for a PPP0E connection. I changed that value to 1492 both in router as well as in Windows and lo! I started to get speeds of upto 55-60Kbps when downloading even when downloading large files from various FileShare Servers. I even got BitComet working with the proper port forwarding thing. But there's a major PROBLEM! Frequently when speeds reach 50Kbps range my ADSL Router (Netgear DG632 connected thru USB) would suddenly disconnect from the WAN port(ie, Airtel)!!! I can still reach the LAN port by logging into my router at & what I see is the Starting page of the Setup Wizard with assigned IP nos & DNS gone and VCI VPI changed to 0,0 (it should be 1,32). Now I go to the Diagnostic page and do a soft reboot of the Router. When new connection establishes everything returns back to normal but with new dynamic IPs assigned by Airtel I can no longer continue with my downloading files. Should I upgrade the firmware for the Router. OR should I get a LAN card to connect with the Router. PLs advise.Thanx