Can an expert explain me why i got google hate?

I have (had!) one of the leading blogs in the seduction niche in france.


But lately a couple, and then today ALL of my well ranking articles and category pages (the ones on the first page of pretty competitive KW's in my niche) are GONE from google!


The site's home page is still first in the rankings for its main KW ("seduction") and ranking well for a few other important KW ... but my ca. 50 other "best" pages are gone !! Only the articles/categories on less popular KW are still there.


The only "borderline" things i did 3 weeks ago were :
1/ send 15-20 links from high pr sites (angela's backlinks) to 4 different pages from the site
2/ tried automatic posting on 10 US social networking site via senuke for ONE of my articles


Also, a couple weeks ago, i installed "seo allinone plugin" on my WP and it changed all of my posts titles + noindexed my categories (cause i didn't understand it had those default settings). But i uninstalled it 48 hours later and all went back to normal in google.


That's it ;


i have trouble believing those actions hurt my site that much. Do i have another problem i can't see (link spamming, duplicate,...)


Thanks a lot