I’m having a similar problem. I can’t uninstall Helloone or even just change to a different theme. When I select a different theme, even the default, I get a blank page. The theme package also comes with two XML files in the app/code…etc/ directory config.xml and system.xml. Could these files have anything to do with it? If I delete those, I get a blank page for everything.
If I could just change themes, I wouldn’t want to delete this theme but it seems like HelloOne is messing up all of my other stores.
I’m using a multi domain configuration of magento and trying to get different stores to have different themes.