If RSSRadio's database becomes corrupted in a way that its self test can't detect RSSRadio may fail to startup.
Under these conditions a "Recovery Mode" is provided to help you.
Open your phone settings app, find the RSSRadio section and there should be a "startup in recovery mode" switch. Turn this on.
When you open RSSRadio you will get a set of options:
1. Try "Restore database to <date>" and restart RSSRadio. This will lose the least data.
2. Try "Wipe DB and restore Subscriptions" which will keep your subscription data but in a completely new database.