Connection goes on and off

I have been using a Linksys wireless-G Broad band router and a Linksys wireless-G card to get the internet on a computer. It was working fine for several months; sometimes the connection would turn off but I would click repair and it would work fine. But recently my internet inexplicably quit. I tried repairing it but it wouldn’t work. I then re-installed the driver, and I had connection for a second, then it switched off, then it switched on, then off and so on. How do I fix this?