Can't access Internet on Ubuntu 9.04

[sham08]

Hello,recently I've installed Ubuntu 9.04 as sole OS on my PC (clean installation).It went well (drivers updated and Internet connection configured properly) for a week.Until,I decided to assign a static IP for my 'torrents' purposes.From that point till right now,I can't accessing my Internet connection.Every time I tried to access,it came back 'Server not found'.Strangely same thing happened when I connected my DSL-520B (the problematic modem) to my brothers HP Notebook on Win Vista.I suspected it went wrong with my action (setting the static IP from DHCP on Ubuntu) that caused the problem to the connection.Please,if there anyone Ubuntu geeks in this forum,that could help me solving the problem.It have been 2 weeks without Internet that make me nuts.Please...