I found a MS Kb about a similar error, saved my REG just in case and changed it, no go.
Another google and i got into this post and this solved the problem. Three simple words, 1 command. Hope it helps you.
Run outlook.exe /resetnavpane
Hello, my name is Pedro Mateus and 'Ponto de Partilha' is 'SharePoint' roughly translated to Portuguese. Since i started with SharePoint and .NET i have found great resources that helped me, this is a way to give to the community something back in return, and keep some sort of a log of stuff i do.
Run outlook.exe /resetnavpane