Hi Gregory,
Very sorry you’re having this issue. I hope we can help get it resolved for you!
Can you confirm you’re running the latest version of our plugins and all add-ons?
Also, can you confirm you’ve tried all of the following?
1. Are you running the latest version of WordPress?
3. Have you tried deactivating all other plugins to rule out a conflict?
4. Have you tried reverting to the Twenty Eleven theme to see if it’s something with your theme?
5. Try setting your permalinks to ‘postname’ in Settings > Permalinks?
6. Try refreshing your permalinks by visiting Settings > Permalinks (it does it automatically)?
7. Try increasing the PHP memory for your website: http://www.dailyblogging.org/wordpress/increase-wordpress-memory-limit/?
I will keep my eye out to see if other users are also having this problem, in case it is a bug or a known issue. In the mean time, if you could perform all the steps above and re-test after each measure, that would help us a lot in eliminating all of the most common possibilities.
Thanks!