WSUS 3.0 - Clients not responding, error = 0x8024400E

Since upgrading to wsus 3 none of my clients are responding to my server. In stead they are failing with below error:

"WARNING: GetAuthorizationCookie failure, error = 0x8024400E, soap clienterror = 7, soap error code = 400, HTTP status code = 200"

I don't know what went wrong, i have tried uninstalling and reinstalling WSUS and have tried switching to another server as well but no avail. My clients are still not responding, is there any one who has faced same issue or has any idea about it??

I wanted to know if you have tried using 'proxycfg -u' command and 'wuauclt /resetauthorization /detectnow' for any of the clients? if not then try using them now and see if your clients starts responding to your server again.