Check the web error log in /webXX/log, same level as the ssl folder for any nasty messages there.
And while I think about it, what browser are you using for this? There have been reports of Firefox 2.0.0 and up doing this with some openssl certs.
I just tested on the ISPConfig/Debian VM image, which has Suexec running, and ZC 1.3.7. Generated a certificate, enabled SSL in the config files, and off it went, no problems at all.