Guy,
We're looking into this. The way we show the user's FB avatar right now is actually on it's way out while we update how we do that. Unfortunately, with the current method, there's no real way to change the link type to open in a new window. With the new system, we're expecting that we can do this easily.
Give me a little bit, and I'll try to get back an answer with a code change in a few days. If it's absolutely urgent to get this going now, just let me know and I can more it up in the priority a bit.
Thanks,
Alex