The last time I tried to use StartSSL, I kept getting an SSL failure on https://auth.startssl.com/... Go figure.
I ended up paying $10 on namecheap instead.
Could save yourself $8 and add a Whoisguard thing to your cart, use promo code WHOISGUARD, and then add the ssl cert.
At least it used to work like that.
Probably an issue with the client cert. I remember running into that the last time I attempted to get a cert through them.
I used to use them. You have to set up an account with a client certificate, which is a pain, then be manually approved. The free certs are for personal use only so they will deny you if they think you will be using it for business of any sort.