A little more information about your site and preferably a link would help here! I have the same problem which is discussed in this topic: http://forums.digitalpoint.com/showthread.php?t=67390 I'm tearing my page appart to identify which part triggers the PSA's. At the moment, I have split it in two and BOTH parts only show PSA's. Therefor I'm going to split them up further until I see which code triggers it exactly.
Check out the keyword you are targetting, check on google sandbox at digitalpoint webmaster tools, if they are showing enough adds for the keyword targetting then just add your keyword in heading and subheading. If it doesn't solve the problem then decrease the number of adds you are displaying on that particular page means if you are showing three adblocks reduce it two if two then reduce it to one and then check it out. Good Luck Sreenivasa