Thanks, that worked for my inficraft problem, but now it seems forestry is being picky. Minecraft stays at the Mojang screen if the latest version of forestry is installed for the right buildcraft version.
Stack trace?
I had to use MultiMC so I can access the error file, is this what you mean:
On the forestry wiki where you DL that zip, it explains succinctly how to deal with that error.