What you are experiencing in my opinion is an epidemic.
Is this an issue with the other search engine? That might give some insight whether this is Panda or not.
My experiences with this situation are well documented already. I'm in the same situation. In my opinion it is because of all the recent algo changes, that now, copied content from your site can easily outrank you based on who is doing the copying.
There is another thread here with a link to a Google doc in which you can submit to them directly, searches that show scraped pages outranking the originals.
There has and always will be scraping and copying. I get that. I accept that. It's only an issue when you are being outranked. Right now it appears that if a good PR site decides to copy, they will pretty much outrank any smaller, lesser PR site. A pretty easy search engine to manipulate. Perhaps the playbook is out there right now. No idea but it's broken. I'm going to bet that the "other" search engine isn't having the same difficulty. Please advise regarding that. We make enough noise, GooG will perhaps realize that something very fundamental has been broken here.
I'll let you know if I come back from it. My situation might be slightly more unique, but I've put some measures into place to break from the scrape. Although they rank for my stuff currently, those link aren't accurate and updated in the results because click those results will ultimately take people to my site. It's a framing issue in my situation.
I think anyone who hasn't been taking their own text and searching in GooG is living with their head in the sand. This is a new problem and most people are oblivious to the fact that it's maybe not them that's the issue here. Duplicate content loss of rankings is nasty nasty nasty.