IOS signin issues

There is a lot of posts about signin issues with IOS devices.
This is the list of solutions:
http://support.microsoft.com/kb/2636320
http://support.microsoft.com/kb/2773530
http://blogs.technet.com/b/nexthop/archive/2012/02/21/troubleshooting-external-lync-mobility-connectivity-issues-step-by-step.aspx

And one not in the list:
Forget wireless network and reconnect.