On my machine, I have a test file where I have turned some artwork into a Scroll Panel. After realizing that the Scroll Panel was the wrong component, I selected it, right clicked it, and chose "Revert Component to Artwork".
Once this was done, my project would not display when testing. In Firefox, I would just get a white page.
This was repeatable on my machine using anything that I converted to a Scroll Panel and then back to artwork.
Hope this helps.
Thanks for the bug report. Would you be able to send us an FXP that exhibits this problem? I haven't been able to reproduce it on my machine so far.
Here ya' go!