Folks -- I don't think this issue is with Facebook, I think there seems to be an intermittent bug with the Facebook app on the Droid.
Here's the workaround for when this is happening:
In the news feed (or wherever else...) long press on the item/friend/etc. to get a popup menu, then touch "View profile". It should work to view your friend's wall as it did before.
This doesn't repair the issue so you can single click in the feed, it just allows you to see the friend's wall in the app.