goodroi - 7:14 pm on Oct 13, 2011 (gmt 0)
I am sorry you are having trouble. I think you might want to invest more into your internet marketing efforts. You say you have a 12 year old site with over a million pages but you don't know how many unique domains are linking to you? That is a red flag to me.
Webmasters should regularly monitor their backlinks. You should pay attention to anchor text distribution, unique domains, unique ips and also the rate of gaining/losing backlinks. This information can be gained by using Google webmaster central or using a paid service.
Backlinks have significant influence on rankings and can also cause penalties. More research should be done to make sure you don't have problems with your backlinks.
Also double check your sever setup. Having multiple servers can create issues if they are not setup properly. Even if they were originally setup correctly a worker might have broken something when touching the setup.