The maven home directory field trips up with a terminal \n character.
Sometimes I get directories and paths using `pwd` in the terminal. In OSX there's a nice utility called pbcopy that will copy its stdin to the clipboard. `pwd | pbcopy` gives you "your/path\n" and although the path is correct, pasting into the maven home directory field inserts a newline character. This gives the alert dialog "The directory you have chosen either does not exist or is invalid."