I don't know what OS you are using ... below is the process to solve your problem in Win xp.
When you try to logon the wireless network, you may end up getting this error message: "Windows was unable to find a certificate to log you on to the network xxxx".
This particular error is normally related to the authentication on a wireless network, usually because the Windows is looking for 802.1x connection by mistake. We can fix it with the following steps.
Click on the Start Menu --> Control panel
Double click on Network Connections
in the pop-up window.
Right click on wireless network connection
, then click on Properties
Now click on the Wireless Networks
tab and select the network in the list at the bottom. Click on Properties
once you select the wireless network that is having problems.
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.
Click on the Connection
taband check the Connect when this network is in range
Click on the Association
tab and uncheck the 'The key is provided for me automatically'
box, then choose Network Authentication & Data encryption
and type in the Network key
according to the wireless settings on your wireless router. Please contact the technician of your wireless router if you have no idea about the information.
Click on OK
and Click on OK
again to save your settings.
As yet, this problem has been successfully fixed, Windows can log you on to the network automatically at once.