The 500 Server Error is probably “Premature end of script headers” (a PHP error message, only visible if are logging 500 errors; I’ve seen it with truncated files, and with too-restrictive file permissions.)
WordPress 3.6.1, Multi-Site, WP Super Cache 1.3.2
This seems to work:
Configured to use PHP caching, Cache Test (on WPSuperCache “Easy” tab): Successful.
Add “Compress pages so they’re served more quickly to visitors. (Recommended)” on Advanced tab.
Fetching [URL] to prime cache: OK
Fetching first copy of [URL]: OK (1.html)
Fetching second copy of [URL]: OK (2.html)
One or more page requests failed:
Page 1: 500 (Internal Server Error)
Page 2: 500 (Internal Server Error)
The pages do not match! Timestamps differ or were not found!
Uncheck “Compress pages so they’re served more quickly to visitors. (Recommended)” on Advanced tab.
Cache Test successful
[note: On my server, WordPress Update hangs, WordPress plugin update hangs, and PHP Unzip hangs e.g. $zip->extractTo($path.’/folder’) or copy(“zip://”.$zipFullPath.’#’.$filename, $destPath.$destName); ]
[Note: in PHP error pages, log $_SERVER[‘REDIRECT_ERROR_NOTES’] to see if there is any error message.]
