I just thought I would post a message to the group for this error for 
posterity.  I noticed that someone had this error a while ago and I did 
not see a resolution posted.  In our case, this error was a result of 
not having the server private key and the signed certificate in the .pem 
file.  All that was necessary to fix it was to concatenate together the 
crt file from our CA and the original server.key file that we created 
into one file which was used as the pem file in the ListenHTTPS line.  
We also needed to obtain the certificate chain file from our CA and 
reference it in the CAlist directive.

Hope this helps someone someday
[...]