If you are getting errors “Pass phrase incorrect” in your apache logs on Snow Leopard server, it is because the key is protected by a password.  I found the answer here.

The password for the key is stored in the System Keychain.  It is a password entry called “Mac OS X Server certificate management”.  You can open the entry and select “Show Password”.  You may also use the security command line tool to dump the password.

security find-generic-password -l "Mac OS X Server certificate management" -g

or

security dump-keychain -d # look in data for password which will look like a GUID

Once you have the password, you can create a copy of the key without the password using openssl:

openssl rsa -in /etc/certificates/server.domain.com.uniqueid.key.pem \
 -out /etc/certificates/server.domain.com.uniqueid.passwordlesskey.pem

You can then replace the password protected key with the passwordless key or point apache to the passwordless key in your /etc/apache2/sites/sitename.conf file.