Recently an error occurred while creating the CSS / JS minify cache…
Frederick Townes, the developer of W3 Total Cache, himself said that the notifications “functionality really gives too many false positives right now and should be disabled.” That was 4 months ago, and still holds true today.
I have this very same error showing up on some of my setups, but the rest are fine, and all this happens on the very same server.
So, I’m afraid, this IS a false positive.