Something I noticed... last month, I modified the template page for the news articles on my website. Basically I cleaned up the HTML, removed lots of useless tags, got rid of nested tables, and other SEO. This affected some 120 pages that used this template. When Google was finished I found that my efforts had yielded excellent search engine rankings for keywords in my news article titles - Top 3 for the keyphrases and in many cases #1. But before that, Google did some strange things. Here is the timeline: 1. I modified the template 2. A few days later, my pages indexed Top 3 for those keyphrases 3. One day later, none of those pages were indexed by Google and they were absent from Google's cache. 4. A few days later the pages showed up in Google ranked in the Top 3 for their keyphrases. I'm writing this because I just did some new SEO on a different template and it appears that Google is doing the same thing. Although I never checked #2, I'm on #3 (pages using new template not indexed). I'm wondering if Google temporarily pulls pages that all of a sudden rank very highly? Maybe when a page that ranked low for keyphrases suddenly jumps near the top it triggers a human review?
I think google noticed some major changes, that's why rank fluctuated. But did the URL of your 120 pages remain the same?