I was having the same problems as you were. I repaired the permissions(which took about 45 minutes) rebooted then expose worked how it was supposed to.
The way that I have it show hidden files and folders is with the program TinkerTool. You can get it from versiontracker.
http://www.versiontracker.com/moreinfo.fcgi?id=11967&db=mac
Just go to apples developer site and create a free account and then you can download the tools for free.
http://developer.apple.com/tools/macosxtools.html
