Comment 33 for bug 828756

It is not possible to ignore SSL errors if you declare your account as a "Google Talk" one.

I managed to declare my GTalk account as a "jabber" one and chose to ignore SSL errors :

Encryption required – CHECKED
Ignore SSL certificate errors – CHECKED
Resource – BLANK
Priority – 0
Server – talk.google.com
Port – 5223
Use old SSL – CHECKED

At least there is no more warning that pops up every 5 minutes.

It is an acceptable workaround for me, but I find it confusing that I needed to switch to a manual "jabber" configuration to do that.