I don't experience any issues with either the stock examples, or with much larger projects, which implies to me that it must be something to do with your system.
I would backup your C2 folder somewhere, then uninstall, delete the remaining folder, reboot and re-install C2. Open one of the stock examples/templates and test.
Also, reset the dialogs from preferences, just in case.
After that, if it still causes issues, then there must be something else interfering, such as dodgy display driver, etc.