I've found an interesting trick how to quickly reinstall ACR and not to delete all of your notes and settings. It's for those who has this bug regulary and needs to reinstall ACR regulary as well. (Windows 7)
Once you see this unclickable lobby - and realize you need to reinstall the program again - just don't close the program, run the uninstallation/installation file immediately. Only when the uninstallation process is finished, close the program the usuall way, by close button, not using your Task Manager. Well you'll have to see their stupid browser ads for a minute. After closing the program and the browser tab you can run the installation file again and then run ACR. All your settings will be saved.