I had a number of customers tell me they were receiving errors when attempting to view or share a PowerPoint presentation via Lync 2010. They would see this error on the Lync Stage:

Some sharing features are unavailable due to server connectivity issues.

In the main Lync Conversation window, they would see these two errors together in yellow bars between toolbar and the call controls:

X Some sharing features are unavailable due to server co…
X Cannot connect to the sharing server.

If they clicked on the “Cannot connect to the sharing server” message, they would see this error appear on the Stage:

No one is sharing. Presenters can share by using the Content List or Share menu.

Other users in the same office were not having any problems, and the same user could share a presentation using a different computer, so the problem appeared to be isolated to the computer or to the user profile. Except that it was happening for multiple users on multiple computers in multiple geographical locations.

After playing with the registry, Internet security, and cached data, I finally just uninstalled the Lync client completely and then reinstalled it. After applying Windows Updates, PowerPoint presentation sharing was working great again.

So what caused one Lync feature to start failing on dozens of computers almost simultaneously? It seems to me that it almost has to have been a software update from Microsoft or our antivirus vendor, but I haven’t compared the update history on all of these workstations. Since I can’t pin down the exact day the problem started, and almost every other computer would have received the same updates as the broken ones, I have serious doubts that I would learn anything definitive or useful. Sometimes it’s better just to get the customer up and working again rather than spending a lot of time on forensics.