One of the other ninjas is working on helping folks get the location contexts working - I think there needs to be at least one active action assigned to the context, you may want to do a google map search to make sure the keyword you're searching against returns some results; there may be other tips as well.
If you could send email to
omnifocus-iphone@omnigroup.com, we'll get you sorted.
If the app is just crashing on open, can you try the steps in this technote:
Troubleshooting applications purchased from the App Store
(though you can skip the part where they ask you to report the crash in iTunes. Also note that reinstalling the app will mean that you'll have to re-send your sync settings, if you're doing that.)
If it's a crash during use of the application and folks do manage to figure out a reproducible set of steps that crash the app, we'd love to hear about it. Once we can repro a crash, we can figure out what's causing it.
One thing to keep in mind is that OmniFocus for iPhone is doing a lot of the same stuff that OmniFocus for Mac does, but it's doing it on a device with 128 MB of ram to share between apps and the OS. If the device runs out of memory, we're going to get shut down. It's possible that something simple like not using the iPod and OmniFocus at the same time will buy you some breathing room.
In any case, we're definitely looking into this - once we start getting crash reports from Apple, and once we get some repro cases for some of the crashes, you'll see improvements.