Codec Error when trying to render
 

Greetings. I am receiving a codec error when attempting to render footage. In addition, I have a grey frame with a "+" in the middle where the screengrab should be in the timeline. Finally, in the viewer, on the clips that will not render there is a black X in a white circle at the beginning of the clip. See attached image.

When I attempt to render, I get "Codec Error" with only the option to click "OK".

Any help?