I'm sort of going through the same thing. I'm still up in the air as to whether or not they're doing a reshuffle or if I'm tanked.
I'm trying to be patient and give it about a week to see if I get back up in rank as I've heard that when they go through algo changes, this can happen.
Looking at webmaster tools, my site doesn't have any red flags raised.
I'm still indexed so I guess that's a plus!