Thanks Jason. It's still happening, but perhaps with slightly lower frequency. More thorough compresses (but still almost never all the way back to state 0) performed more often have seemed to make things slightly better.
Since my last post, we've discovered that one editor (out of six) has never once encountered the "z value" error while reconciling. The rest of us, though, all seem to encounter it at the same times (very roughly once per week). Interestingly, I wrote some ArcObjects code in '07 or '08 that automated some of the version management for our users, and the one unaffected user has never used these tools while the rest of us have. But if my code is the problem then why only after three problem-free years, and why only sometimes? I'm not afraid to blame my less-than-stellar .NET skills for this, but there's gotta be another contributing factor somewhere . . .
I can ship you whatever you want, so sure you can have some data. But since we're not sure what's causing the problems (at least no one on my end is), would this have to be a copy of our entire SDE database? That won't fit in an email. 🙂
Thanks,
Dan