We've had some success with this issue. After having installed Sitefinity on three systems, it worked on one.
System 1: Win 7, MySQL 5.6, Visual Studio 2013 = MySQL error on launch
System 2: Win 8, MySQL 5.6, Visual Studio 2013 = MySQL error on launch
System 3: Win 7, MySQL 5.6, no development tools = Sitefinity launches!
Currently I don't have more granular details on what is causing the failure. The two development systems have Oracle's MySQL .Net Connector installed which is needed for working with MySQL in Visual Studio / .NET