Losing internet connection

Hello,

I recently had to install a new router for my cable internet connection. Everything was working great at first (and with the old router I never had any problems until it died) but when I put my Mac to sleep and then start again, the internet connection is gone. I have to restart every time to get back onto the internet. Now, the connection just gets lost if I take to long to do something without actively using the internet, like writing an email. In fact, I am really hoping it lets me send this out... I went into the keychain to delete the old router, and now there is nothing there at all, the new router doesn't show up.

Help Please!!

Thanks