While I'm creating a design it won't let me make changes. It keeps telling me the file is locked and other errors. To get past it, I constantly have to save my file. Sometime that doesn't work and I have to click save as and let it overwrite the file. But sometimes that doesn't work either and I have to close and reopen the file or even save it with a different name.
Have you tried running FW in compatibility mode? FW CS5 is old, and was not written with Windows 8 in mind.