It looks like the code we use to verify SSL certificate chains is very picky about the order of the certificates in the chain, I'm not sure if I can edit it to remove this dependency.
In this case the chain is
itanican.com
COMODO RSA Domain Validation Secure Server CA
COMODO RSA Certification Authority
but they are being sent from the server in this order
itanican.com
COMODO RSA Certification Authority
COMODO RSA Domain Validation Secure Server CA
Is it possible for you to change the order of the certificates in your .pem file?