FWIW, I emailed Pandora about this issue, thinking at least it would let them know that one more person is troubled by this. They responded with this:
Dear StatusCheck:
Sorry you are having problems with this.
My first suggestion is to power down the phone and pull the battery out. Put the battery back in, turn the phone on, and then try launching our app again.
If that doesn't help, try uninstalling then reinstalling the app.
>From the home screen, press the menu key and select "Settings" then "Applications". Next select "Manage Applications". Scroll down and select Pandora. Then uninstall.
To reinstall, go to the Android Market and search for Pandora. You should also see it in the most popular apps list.
Note: We do not support Pandora on rooted or modded phones, unofficial OS releases, or custom ROMs. We only support Pandora on configurations that we have fully tested, so as to ensure the application will work correctly and won't cause any problems with functions of the device.
Let me know if this helps.