Even_Steven - 7:30 am on Sep 25, 2010 (gmt 0)
You might try refreshing one of those pages several times over and over, to see if AdSense always display a PSA. If it always display a PSA, then you know its a contextual relevancy problem.
If sometimes it shows paid ads, then you know its a problem with not enough paid ad impressions available.
I wonder if AdSense has a flag that can be set manually to identify sites as being "adult oriented" considering you have a lot of photos of female models, and you used to have a lot of questionable text. That kind of flag would allow advertisers to block their ads from displaying on such sites. If you can get ahold of someone at AdSense, perhaps you could ask them if this is the case.