80% of the time when opening a Finder Window it's completely blank and I have to relaunch Finder from the Force Quit menu several times before it starts showing files again.
I'm having this problem, too! Are you using Adobe CC? My MacPro and MacBook Pro both have Adobe CC installed and are having this problem. My wife's computer, also on Yosemite with no Adobe apps, and the finder appears to be working fine.