You can also flash the same firmware of Tomato USB as described for WRT160N_v3.0 I had an awfully difficult time doing serial recovery on this router.
It was my first time so you can imagine that I had no idea what I was doing.
Then go to "authentification" tab and untick the box saying "Enable IEEE802.1x to the availiable network" and that should solve your problem Graham UKRight, Graham's solution worked for me.
I had been able to connect previously, but the connection would always indicate that it was validating.
Wait until both wireless and power lights are on steadily, then navigate to in your browser of choice again.
Click on the Authentication tab and now uncheck the Enable IEEE 802.1x authentication for this network box.
If the box was checked, then that was why you were getting the “unable to find a certificate to log you on to the network” message because Windows is looking for one, but your wireless router is not setup for certificate security. Once I unchecked that box and tried to reconnect to the wireless network, everything worked fine!
Also, since I was able to connect from my laptop with no problem, it led me to believe it was something wrong with my desktop.
After about 30 minutes of fiddling around with various settings, I was able to figure out what the problem was.