It's not all about Google Page Rank
First off don't worry about PR I have over 20 sites with PR1 and 0's beating PR's 4-7. It comes down to how good is your content, and the quality of links you have.
Avoid Thin Content, Merge Pages and Make Better Pages
If you have a 1,000 Articles then the chances are they are considered THIN by Google, have you checked to see if these pages are THIN? Less than 400-300 words each? If so you should strongly consider merging some pages together to improve the user experience of your visitors and Panda will like you for it.
Now I don't mean merge a page about cats to a page about dogs but I think you know what I mean.
If you have 6 pages about Cats, Merge them! offer more content on the page and actually improve the experience your visitors have while visiting your site never mind they will remain on your site for longer.
In a nutshell Google wants rich experiences say hello to Panda
Google's Panda is all about slapping sites that they believe are not returning visitor experience, duplicate content if any is an experience they can obtain else where, thin pages have been abused by webmasters trying to get Google to give them Authority on a Serp, IE a site with 1,000 pages about Cats would like have more authority than a site about cats with 20 pages, this is no longer the case and many factors are brought in while before they didn't. It's possible whit a small site to outrank a larger site, well actually I believe its easier if you stay on topic.
Authority is Important
Take amazon for example, they are trusted by Google's lots but if I type Cat Leads into Google, Amazon is not top even though they have more pages, more pet items, more back links and so on, Pets at Home are top for me, this is because the Word Pet, and The authority gained on the Word Pet.
So while your rankings may have dropped its not always Panda to play, they are stomping on sites that are trying to dominate all serps, and never mind localization is coming into effect more aggressively every day.
Google loves REVISITED content
I would start at looking at the content itself, use copy-scape site to check for duplicate content, check webmaster tools for duplicate pages/titles/metas, thin content (CHECK THIS MOST) and check the Google's Panda, and Penguin what they look for and see if you can fix things.
Good Luck and I hope this helps you out :P