1script - 3:52 pm on Sep 5, 2012 (gmt 0)
What type of changes are we talking about? Not sure if you meant a benefit to users or you've actually benefited from a traffic increase (huge, no less). But since this sounds like some dramatic changes have been done, it would seem reasonable to look at those as a potential culprit. The timing is also right.
A couple months ago I de-optimized my site to huge benefit
So, what did you do?