incrediBILL - 10:04 pm on Aug 13, 2010 (gmt 0)
OK, I think I resolved my own problem and now CTR is actually HIGHER than it's been all week, insufficient information to blame or attribute the new layouts to anything yet, still watching and tracking trends.
Fixing the targeting issues, considering nothing on my pages had changed, turned out to be as simple as reloading the problematic pages multiple times until it summoned the mediabot crawler to finally come back to the site and re-read those pages.
After the mediabot visit, VOILA! all the pages went back to normal targeted ads almost simultaneously.