Hello Todd, I’d be happy to help you with this – sounds like an intriguing puzzle to solve 🙂
Thank you for noting the versions of the plugins and WordPress you are using. In order to rule out all the more “common” causes of problems, can you tell me if you’ve tried all of the following to see if it helps fix, or at least identify, the problem?
1. Have you tried deactivating all other plugins to rule out a conflict?
2. Have you tried reverting to the Twenty Eleven theme to see if it’s something with your theme?
3. Try setting your permalinks to ‘postname’ in Settings > Permalinks?
4. Try refreshing your permalinks by visiting Settings > Permalinks (it does it automatically)?
5. Try increasing the PHP memory for your website: http://www.dailyblogging.org/wordpress/increase-wordpress-memory-limit/?
Thanks!