Tonearm - 6:03 am on Sep 25, 2012 (gmt 0)
What version of Piwik are you running? They've allowed you to create reports using a date range for a while now. Maybe you just need to update your Piwik installation.
Thanks, I'm looking in to that now.
Check backlinks, maybe someone is maliciously attacking with penguin-esque links to drive your page down. (Although if "widgets" is still ranking high as opposed to "blue widgets", it would be a term based penalty, so check for exact anchor text). Usually when only one term drops it must be a term based penalty, which in the past related to exact match backlinks or over-optimization of on-page stuff (keyword stuffing, etc.)
I've been suspicious of something like this from the beginning. I've never done any link-building so I'm not sure how to do about checking into this. Is there a good and free online tool, or should I subscribe somewhere?