I noticed when I did the packet capture that the SSL certificate being issued from Google is from Thawte, but the iChat config instructions on the Web site say to allow self-signed certificates.

Could Google have changed certificates without telling anyone, and iChat is balking at the change? Who knows.

More on iChat's SSL:

http://edr.euro.apple.com/documentation/Security/Reference/SecAppleTrustPolicyModuleSpec/Apple_Trust_Policy_Module_Functional_Specification.pdf