That could be caused by an incomplete uninstallation. Please make sure the installation directory (e.g. C:Program FilesABB RoboticsRobotStudio) is empty before you reinstall the product.
If you revert to an earlier version you should also uninstall RobInstall before reinstalling RS.
A colleague of mine is now suffering with the same PC lockup problem as me. This only happens when connected to the network. I note that we have both configured the ‘IBM ThinkVantage Access connections’. is this to blame?