Thank you Mike, I'll try to do that then.
We have also cleaned some suspect backlinks from some old-time-directories that could have had some weight for our latest loss. Even though we had links there for a long time (several years), we have considered the fact that Google could have updated his algorithm to account for those bad links in some way and discount most of our rankings.
To give you an idea of the loss I am talking about, have a look at our SEO visibility on searchmetrics.com:
http://suite.searchmetrics.com/en/research/?se=1&url=www.virtualsheetmusic.com
From the end of June we have begun to have a big drop in traffic, we have lost around 30% traffic from Google. That could be due to some algorithm change either content side (Panda) or link profile side (Penguin or similar?). We had some Panda related issues in the past, so that was the first possible cause came up to my mind, but since we had very big drops on some major keywords of ours for which we built suspect links in the past, I also thought about a possible Penguin related problem.
Thank you for your thoughts on this!
