tedster - 1:28 am on Jun 29, 2012 (gmt 0)
I'm not so sure that you need to be able to say definitely if it's a Panda punishment or something else. Bottom line is that you know your review section is getting a lot less traffic, and I assume this is an important section for your business.
So I'd say dig into the analytics for the review section a lot deeper. I'd be checking the rankings and the search traffic, page by page, for the losers (hopefully you've got historical data so you can compare). If you can do that I'll bet some insights will start to pop.
The other question I'd ask is if you made any changes to the internal linking and navigation - anything that might have cut off the flow to the review pages a bit.