Error attempting to render file

The dialog basicly says, that a file from the frame cache couldn't be found.

This is not really bad since AE can rerender that particular image information.

Can you just click OK and does the render start/continue?

Also try to completly delete the folders in the cache up from this path:

/Users/gregkinne/Library/Caches/Adobe/After Effects/

The last option should resolve the issue.

If you are getting errors like this frequently, check your hard drive for damaged/dead sectors.

*Martin