I'm having a similar issue with just one EMD on a competitive phrase (I manage others and no issues). It ranks no 1/2 on Bing and is currently down the lowest I have ever seen it on Google at page 21.
The site was managed by another company this time last year who ran it into some Panda issues around the end of April. I had since re-structured the entire site and re-written all content, and it slowly worked its way back to page 2 for the target term. Then recently the site started nose diving again. The site is so clean now which is the frustrating thing.
I'm not to blame for the original issue (they added around 30,000 product pages of thin / duplicate content) but I really thought I was getting somewhere and could save the site. I'm now questioning the EMD issue as it's squeaky clean.