Hey our super-fab Mod Angie Newton posted a thread over on the Elite side about her blog links breaking after she upgraded to WP 3.4. Turns out she uses this permalink structure: /%post_id%/%postname% as recommended by Lynn. I use it myself, so I helped her troubleshoot.

It looks like the upgrade to 3.4 breaks the short version of the links. So http://yourdomain.com/1234 will no longer work. You'll have to use the whole thing.

Just FYI. I'm going to look into it a bit more to see if there's any word from WP. Will post back as I learn more.