On the dev launcher, sometimes, its screen becomes black, as if it froze. It usually happen when Java runs out of memory, with the game loaded, and the launcher as well. Also, the launcher used, when it was black, about 138 000 kbytes memory ! To fix it, you should add a tab to select the memory you want to allow to java (void's wrath launcher got it) and shut down the launcher if Java run out of RAM.