Welcome to the forum.
It sounds like an incompatible video codec, is this file any different from what you usually edit?
And, perhaps there was an update of your graphics or OS that is playing poorly with your file.
Try rollling back your graphics card driver, or unticking any hardware accelleration in Prefernces.
HP Envy Phoenix/4thGen i7-4770(4@3.4GHz~turbo>3.9)
Nvidia GTX 960(4GB)/16GB DDR3/
Canon Vixia HV30/HF-M40/HF-M41/HF-G20/Olympus E-PL5.
Tape capture using 6 VCR, TBC-1000, Elite BVP4+, Sony D8 camcorder with TBC.
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