I ended up with this exact same error. I'd been happily following Wuppy's new tutorials for 1.8 (http://www.wuppy29.com/minecraft/modding-tutorials/forge-modding-1-8/) and decided in my infinite wisdom to rename the location of my root Forge folder from c:\minecraft-1.8 to c:\forge-1.8 (I'm on Windows). Well, after doing that the project sort of loaded but it couldn't find any of my source files. More frustrating was that it was still broken after renaming the folder back to c:\minecraft-1.8! Cue several hours of totally deleting all directories and instances of Forge and Eclipse, including those pesky .gradle and .eclipse folders on your user and AppData directories. Still no joy. Completely rebuild using gradlew cleancache --refresh-dependencies setupDecompWorkspace eclipse . Nope, still not working. I even tried setting up Forge 1.7. But then I had an epiphany. I'm a NodeJS developer for a living and use the Git Bash console for git actions (it's a MINGW32 console). I re-ran the gradew command in the Git Bash terminal, which took a few minutes longer than from the standard CMD terminal, and voila! All working again.