Are you enjoying Diablo 3? I sure as hell am…see that? Well, I hope your experience has been going well. We want you to keep having fun so we want to make you aware of a bug if you haven’t already experienced it or have seen it yet floating around. According to a many posts in the Blizzard Forums, equipping a templar follower with a different shield may result in the game desynchronizing from Blizzard’s servers. Some users have also said that after this encounter they are unable to log back into Diablo 3 – they are specifically encountering a timeout error 3006 – even after restarting the game.
Apparently the issue arises specifically if you swap items that you currently have equipped with the Templar. Still, probably safer to not mess with a Templar’s equipment at all for now.
Heads up, and Happy playing!
Source: Blizzard Forums(1), (2)