I'm extremely pleased to announce that the final Doors CS 5 bug has at long last been found and eradicated. The mysterious crash of certain large Ion programs was explained by the simple fact that executing above $C000 crashes any TI-83+ or above. I solved this by putting the Ion library includes at the very beginning of the Doors CS source code, and all of the programs that previously crashed are now working perfectly. I will officially release the 5.1 Bug Fix tomorrow morning. Until then, wait in eager expectation or think of features you want for Doors CS 6.