I am having the same problem, and traced it back to my use of "Spaces". As soon as I assign the Finder the "Every Space", its windows are not coming forward when switching to it (with Command-Tab or the Dock).
Assigning the Finder to a single Space, or removing it entirely from the Spaces preferences "solved" the problem for me. Of course a solution which would allow me to bring Finder windows forward, while still using them in all Spaces would be preferable... Any ideas?