You're not a very verbal one, are you?
My impression is that whenever the app suddenly kicks you to the home screen, that's just you cue that it crashed. I.E. the answer is that they have bugs in them.
um... that's called crashing? and bugs? i didn't even get to load 'where' once.. they all stopped together...
Are these 2.0 "official" app store apps, or 1.1.4 Installe.app apps? I don't have experience with 2.0, but yeah, at least with the installer.app apps, that's exactly what it means. It happens to me sometimes with Twinkle and iFlickr.... You might try rebooting your iPhone if you haven't yet... that helps sometimes.
I have the same problem here... all 2.0 apps just take you back the home screen. Have done a hard reset 2 times and it has not fixed the problem.
If all the apps crash all the time, you may need to consider just reflashing the firmware from iTunes and starting over...