I have had this problem only with snapshot 13w23a/b and it doesn't seem to be happening with anything else. I have tried reading in the console and it said something about having multiple arguments for the version to run. It also said something about a file not being deleted, so I deleted it manually... still didn't work... any help?
Edit: l think I fixed it, have no idea how, but I did...
Edit: l think I fixed it, have no idea how, but I did...