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Seems like it could definitely be over-optimization then. That doesn't seem like a natural link profile at all. See if you can get rid of some of the lower quality links, and focus on getting high quality links with varied anchor text.

Hello Willem, Yes, in my opinion you should submit languages. I'm not sure but think that main site on .com should be set as basic NL site. For each sub-site (language ver) sitemap in particular language is needed, I have no idea how your sitemaps are created. If on automatic way (plugin or other way) it seems to be a bit complicated, but it's better to have sitemap than not to have, it is worth your effort. Use meta tags "alternative" in section on each site. And ... ask other people, maybe there is something new. Theres a lot of stuff in the GWT blog and forum... Marek