Maybe he looked pained because he finally realized he just isn't funny, his routine wasn't funny and his entire schtick is tired and worn out. Had I watched the awards show, I'm sure I would have had a pained expression, too.
Actually, there may be no accounting for my taste, but I thought the toned-down routine WAS funny. It's just that he was delivering it terribly---it sounded more like a lecture. If he had only pulled the stick out of his butt it could have been fun. I mean, come on, who couldn't laugh at "Spongebob Hotpants". :)