agree with everythings that ist told here - hotlinking may be a problem. But: in my experience in most cases the text is the problem - even if you think everything is fine. There is something like a hurdle - if you are under no problem. But if you have one word too much the hole site falls in the seafesearch filter.
So I would recommend to search on your domain for topics like "sexy", "hot", "adult", "explicite", "sweet little", "lipps" and so on... Change all these words to harmless synonyms. Using the site-command could be helpfull:
"site:yourdomain.com sexy" and so on ...
If you are sure that everything is Ok, go straight to the Webmasterhelp-forum and tell them that they fail: -> [productforums.google.com...]
Good luck, Martin