I have the same issue on launchbox on my arcade cab (key 5 not present). Tried two different computers (one a lightweight, the other a gaming rig), totally fresh installs (purely default settings across the board, imported 250 mame roms is the full extent of the current game list), computer isn't the problem. Scrolling the games list is an insta-crash. Maybe it doesn't like forced 4:3 aspect ratio on a portrait monitor? Bigbox works fine, but its a pain for playlist management compared to launchbox.
Is there a place to get an older working rev of launchbox?