I'm sorry that you're having trouble with KnitMinder. The only thing that should cause the app to shut down like that would be an incoming phone call or your battery going dead, but I'm sure you would recognize both of those cases, so it sounds like this is probably a crash in the application itself.

When an iPhone application crashes, the phone's operating system stores information about what caused the crash in a file and transfers those files to your computer when you sync your phone. These crash logs would help me quite a bit in locating where the issue lies and how to fix it. I've written up step-by-step instructions on how to locate these logs on your computer here. If you are able, can you send me your crash logs so I can take a look?

Regarding your other question about grouping patterns by type: this feature will be part of KnitMinder 2.0, which I'm working on now. I don't have a release date yet as there is still a lot to do on the app, but you can keep an eye on this site for announcements on when the new update will be available.