[analog31]

One thing I've learned is that managers hate surprises, and hate making decisions in front of an audience. Think about how it feels to have your idea (going to the conference) vetoed. Their idea (approving your attendance) could get vetoed too. The easiest thing to do with any unexpected idea is to quash it.

Perhaps a way to deal with a situation like the conference, is to get them involved early. Like, before you apply for it: "Hey, boss, there's this conference that I think would be beneficial for us. We'll learn a lot and if I give a talk, it will be prestigious for the business. It's a long shot, but can I apply for it?"

Also, in all conversations with your boss, work on your mutual enthusiasm for your career development. At the very least, it's unlikely they will say to your face that they don't support your career.