I've been logging a lot of hours with Skyrim lately. As of today (6-20-13) I began getting "Steam was unable to synchronize your game data..(etc.)" I havn't logged into Steam or played Skyrim from any other machines. If I click through the error, the game checks for mod updates until reaching 3 new mods I had recently subscribed to. It then feeds me the "Unable to download subscribed mods Steam error 16" code for all 3 mods. Playing the game runs fine and my save files are unaffected.
It does not appear that my issue is being caused by any of the topics listed there, as my steam connections elsewhere (discussions, the workshop, friend chat) are all working just fine. Any help would be greatly appreciated.