Windows unable to find certificate to log onto wireless network

Hi
First time on this forum with a serious problem:
At work I usually can tap into the network by just plugging the Ethernet cable. The DHCP-Server does the rest. Now I cannot log on any more and windows delivers this error message:

Windows unable to find certificate to log you on to the network

I have browsed the net for solutions (IEEE and so on) with no avail. Wireless encryption problems don't apply. A colleague with a Mac manages fine. At home i plugged directly into my router - same problem. I have installed a backup of the entire system with no result - so the problem cannot be on the software side.I have now even bought a pmcia ethernet card to exclude a hardware fault of my ethernet adapter - still no result. and by the way - my wireless works fine!

So, with other words - if there isn't some super crack out there with a solution, my notebook (ASUS W1Na) hass seen the days of Ethernet communication.....

As far as i know the Error you mentioned above is related to wireless networks. I guess your system is somehow continuously trying to connect wirelessly to some network and probably your NIC is set to disabled. Are you getting the same result when you plug in the cable at home?

Until you reply, just go through these steps and see if it works: Right click My computer, select Manage and click on Device Manager from the left bar. Is there any Yellow mark infront of any device? Also when you go to Control Panel > Network Connection, what you see over there?

Thks for the reply

Device manager etc. is all ok, hardware is all working and drivers in order.
On another trile at home the system roll back seems to have worked and I can connect directly to my router without problems.
The problem at work remains though.
As I said, my colleague with a mac connects - I gt the message concerning the certificate. After half an age an IP 169.254.152.125 is assigned and the local area connection status reports 0 bytes received.

Any help?