With the just released version 5.2.34 we also changed the python version used in MySQL Workbench (to 2.7). However, this produces a problem when upgrading from 5.2.33. The reason is that the installer leaves all the compiled python files (*.pyc) in the installation folder. On next load of Workbench you can’t even get beyond the splash screen.
We will soon publish a new release with that problem fixed. In the mean time simply uninstall Workbench before you install 5.2.34. Your stored connections, starters, settings etc. are not touched by this. Make sure that you remove any remaining file once uninstallation finished, before you install 5.2.34.
This problem was first encountered on Windows using the msi package, but might also affect the zip package or even other platforms. In any case remove the old files before installing 5.2.34.