I have a net gear DG 834G wifi router and connect two laptops and a desk top to it.
Recently had a bit of bother with the whole system and had to start from scratch and since then the computers do not always automatically connect to the net. They do sometimes!! When they don't we have found that if we type in the routers address 192.168 etc and go to the basic settings and merely scroll down to the test button, in a few secs we are informed we are successful connected to the net!! We have changed no settings at all in the process.