Have you built tons of links in a short space of time? If so, it may be just a google dance until its settled. Many of my sites have gone to page 200 after i had built thousands of links to certain pages, but it would always return to the first page within a few weeks. Just build the backlinks a little slower and get backlinks that actually have pagerank rather than spamming blog comment and profile links. Im not saying that your spamming, but these are genuine reasons why people lose their ranks.
Tried it a few times, sites where pushed 100-200 pages back when searching for their keywords. Even when searching on domain name my sites where on page 10 or something. I removed the bad content, added some fresh unique and built a few manual high quality backlinks over a few months. Took around 3-5 months before my sites where back to normal. From my experience, its either due to really crappy content or if you buy to many crappy backlinks on new domains. (Dont go those 1000 cheap backlinks on new sites, will hurt more than doing any good )
Hello, You can also request for reconsideration if you fixed the issue for which your site get banned. Thanks