I had half of my sites (about a dozen), banned in march.
I noticed it when the traffic dropped and the sites stopped ranking for their domain name or site:domain name searches.
However, they still show PR, they are still being crawled,
Same here, at least they did for a while.
I spent many hours going over my (diverse) sites trying to find out what went wrong with no success. I filed a few reconsideration requests, never received a meaningful response. One thing my banned sites had in common was adsense.