[JKT]

I honestly don't know - I have both those and no issues with playback. Flash has always worked fine for me (latest plug-in)... that is, when I actually allow it to be displayed ;)

Try temporarily moving the Quicktime and Flash plug-ins out of the /Library/Internet Plugins folder to e.g. the desktop. Quit OmniWeb if it was open, then re-launch it with the plug-ins absent from the folder - do they disappear from the list in preferences? If so, quit OmniWeb again and add the plugins back. Does this restore functionality?