I get an error There was a problem acquiring a personal certificate required to sign in. If the problem continues, please contact your support team. I'm using Windows 7 and have an office 365 account which is where Lync is hosted.
I've tried all the troubleshooting and no joy, also doubled check if there is a Lync certificate in the personal store, and none located.
See original post http://community.office365.com/en-us/f/166/p/289095/882945.aspx#882945