On the Mac I exp crashing like I never before have. After every line of code I right , once I press add action , I go to the file and save. I save at least 3-5 every 10 minutes. No one here can actually stop that bug except Akr. Also if the game is reading another font , even though the one you choose is in data file , you will crash like its liquid water and you wont know why.
Sometimes its best to concentrate on what does work. Thats what I would do.
By the way I added yvelocity++; and no crashing.