Thanks for the crash log. It looks like a database corruption problem.
The database file is at [your home folder]/Library/Application Support/NetNewsWire Lite/Articles
Here's what to do:
1. If you have a backup (via Time Machine or some other way), you could replace the Articles database with a backup from before the crashing started.
If you don't have a backup, you could delete the Articles database.
2. Also delete the following folder: [your home folder]/Library/Caches/NetNewsWire Lite/
The drawback is that you'll have items marked as unread that you've already read. But once you get caught up, it will start working normally again.
Sorry about the crashing! It's the first I've seen of this bug, so I will be investigating further.
-Brent