Why doesn't Apache log startup errors on Windows?
I found the cause of the problem simply by typing httpd on the Windows command line:
c:\>httpd
Syntax error on line 56 of C:/Program Files (x86)/Zend/Apache2/conf/extra/httpd-ssl.conf:
SSLSessionCache: Invalid argument: size has to be >= 8192 bytes
Still wondering why this is not logged to error.log, but at least I now have a way to know what's wrong.