Had the same issue. If you're running the Steam version, try this:
End all Steam processes in Task Manager.
Go to C:\Program Files\Steam (or the Steam directory that was specified during installation).
Locate ClientRegistry.blob and rename this file to ClientRegistryOld.blob
Restart Steam to allow the file to be recreated.
It still took a little while to start on the first try, but I've been able to launch everything since I've done this.