Under network manager, select edit connections, under the wireless tab select the connection to your router and select edit.
It struck to me that Android phones have tethering option.
I plugged my phone (Google Nexus)(it works with S3 too) to the Ubuntu System and Turned on the USB tethering option and viola I got a great wired signal and was able to browse and download stuff again from Ubuntu m/c.
That solved my problem temporarily (until I find a right driver or new wireless adapter that works for Ubuntu). Now remember you will need to do this to each computer that is having issues.
This question might not be directly related to problems in Ubuntu, but I am still posting this here because it is possible that someone might know of a solution.
I am using Ubuntu 12.04 and am using a Belkin N150 wireless router to connect to the Internet.
It seems that there is a problem with using Belkin N150 wireless routers.The Internet connection is very flaky, and the connection drops frequently for a few minutes before it is again re-established.I found the following link that discusses how to solve this problem on other non-Linux platforms. It would help if anyone can suggest ways to solve this issue on Ubuntu.I cannot answer this question directly, as I have no experience with this particular router; however, the answer in the link provided for windows 7 would basically be the same for ubuntu.The only difference would be using the network manager to setup the nameservers.