I think I've had similar problems, slapd was giving a certificate related error for me so I followed the info here
Recreating a Self-Signed SSL Certificate - Zimbra :: Wiki (i think) and removed the certs and replaced them with selfsigned ones. That allowed everything to start up ok and from there you can try to get the real cert back on. It's not a fix, but if you need to get the server up then it should help.