I'm having the same issue on the Roku streaming stick 3810: theAll4 app crashes when it launches to the home screen. I found that if I quickly scroll down to categories, it stays open, but if I scroll back to the home page, it crashes. Also, if I log out of the App, it launches without crashing. Strikes me as maybe the login and sync process might be pulling too much on the ram/cpu of the Roku stick.
In my opinion, this is an issue for the app developer to resolve with Roku support, and it would be well worth Roku getting it sorted out because this is a very popular app.
I found this too and you can also quickly scroll up to My4 and across to My List or History, just avoiding the "Watching" menu item. It seems that the currently watching content might be the problem because that appears on the home screen also. I aso found that the app doesn't crash on the home screen if logged out, and obviously there's no "currently watching" option if logged out.
I have the same problem since a couple of weeks ago with my Roku Express. All4 crashes upon opening. I've tried all the fixes suggested in this thread. If I can't sort it I'm going to replace it with another brand of device - All4 is my favourite channel and I really hope Roku will do something to sort this out.