When 'Preview' or 'QuickTime Player' start getting flaky about opening, I find that tossing the App's saved state, as found in the 'Saved Application State' folder of the user library*, usually fixes the problem.
A crashed state is sometimes saved as an App's saved state. That makes opening the App problematic. Eliminating the corrupt 'saved state' gives an App a fresh start.
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* User library is invisible by default, so enter ~/Library/Saved Application State in the Finder's 'Go To Folder' 'Go Menu' Dialog.