February 6 Update: (Happy Birthday Sophia!) After writing this post, we posted the 14.0.4 update for the Lync for Mac client - http://support.microsoft.com/kb/2778095. The customer and I are still monitoring his situation but initially it looks positive. The true big bang with this update is support for more devices. Justin Morris also blogged (http://www.justin-morris.net/update-14-0-for-lync-for-mac-2011-released-now-makes-all-usb-audio-devices-work/?utm_source=rss&utm_medium=rss&utm_campaign=update-14-0-for-lync-for-mac-2011-released-now-makes-all-usb-audio-devices-work) on this topic and links to the download article
I had a customer issue where Lync for Mac 2011 was failing to join meetings in our Lync Online Dedicated topology. They shared logs and I felt it was likely a keychain issue but then I was able to reproduce the problem at home on my MacBook Pro. The local repro allowed me to review my network settings and log file closer and after searching I used the following 2 articles. The customer followed these article also and was able to login, we will monitor over the coming days to be sure. Both the customer and I had taken the Keychain troubleshooting tasks before with no success so he and I are thinking the DNS FlushCache is the likely solution.
I flushed the DNS Cache and removed the Keychain entry. Of note I also went through every entry and removed any certificate showing with red X’s.
I skipped step 3 which was the uninstall part of the article and simply deleted all the various file references. An interesting item I would say is that I tried to delete this keychain entry (OC__KeyContainer__<e-mail>) above and it prompted for credentials never deleting it, somehow during this step it worked. I can only think that I did this in another manner or possibly Lync was still running the first time.
I am following up with our content teams to try and combine all the information along with my notes in order that we have 1 all encompassing list of options. As well the customer and I will be testing and if possible do our best to track it down to what we think is the minimal steps to take to resolve.