Sit bone pain after ride...suggestions?

Your position sounds off on the bike.  Or if it is right, you are moving out of position while riding.

Or as Carol mentioned, may not be enough time in the saddle.

I've been riding since July and have 718 miles so far.  Not a lot, not a little.  The pain is a deep (think Ace Ventura, when he has a spear in his leg, and he's yelling, "It's in the bone, it's in the bone!!...that's the thought I get.  ) substantially debilitating but short term issue.  As you mentioned though, it's an a$$ issue, as that is all that hurts.  My legs feel fine.  Bending over to pick up running shoes is not a lot of fun.  That's where I REALLY feel it, so perhaps it's a flexibility issue as well?  When I start to run I feel like my (boy, this gets TMI quick) butt has to align itself in order for me to run better.  I'm also thinking Daremo might be right about me getting out of position somehow.  Unlike you keyone, I stay in the same position longer outside than on the trainer, as I get bored on the trainer, hands get numb, and I have to fidget.  I don't experience those things on the road.  Between trucks, deer, hills, and impending darkness, I pretty much get in one of two positions (on top of bars by shifters or in the lower handles) and ride as hard as I can.  I knew I was a little tense due to darkness and hills last night when I got done and my right forearm was pounding from gripping so hard. 

I may have been anatomically incorrect.  Where you describe sit bones is exactly where the pain is.  Yes, I did have a professional fitting, but it may be time to go back and get tweaked.