This kind of trouble is new for me but it lasts 'til 9 months now. Therefore I ask ...
Got a site from a client last december who was not present in G SERPs for his main (category) KWs and for specific 3-word keyphrases.
Took one of his many domains (which was a secondary domain before = pointing to old main domain). Put old content of category pages there, and a lot of new content at deeper pages. Set up new domain at another IP, redirected old one (301).
2-3 weeks later at page one in G for main keywords (categories of website).
Another 1-2 weeks later: buried around 200 and deeper for main KWs. Little movement until now. (For same category KWs good rankings in Yahoo, some time later. Good at G for KW +very frequent word, too.) At the other hand top positions in G for 3-word-phrases (related to that new content deep pages).
Tried a lot, clueless at last.
Then my client liked to inform me that there were other domains - some with the same content as that category pages (which were buried) - , and some just redirecting w/o some 301 stuff or so. Some of the latter had bad inbound links (link farms, PR zero - my client said he had another SEO specialist before ...).
I had a lot to clean up, and I'm not sure if I know everything he or somebody else did in the past.
Here are my questions:
Would you continue? (he's paying, though ...)
More important: Supposed I've cleaned up everything - will the site come up? How long would you think it will take to come up?
Does it any harm that the site is well optimized with on-page factors, some inbound links - not too much until now (I'm chary with that until I know what's gonna happen ...)
Should I build a new site? If so: has the content iof category pages to be changed?
Ah, I forgot: He's doing a lot in Adwords for his main (category) KWs.
Right now he get 55% conversions from Adwords, 45% from SERPs (Google related - Google conversions together are 57% of all conversions).
THX for sharing your experiences.