Since I've upgraded to Piwik 2.0 (using the automatic upgrade process), there is nothing displayed in the "keywords" and "referers" boxes ("no data for this report"). But the problem is very confusing:
Upgrading to 2.0.2 did not solve the issue.
Keywords: keyword, referer
Thanks for report. I haven't seen or heard this issue before. Are you seeing any error in your server error logs? Have you setup the cron as explained in: http://piwik.org/docs/setup-auto-archiving/
This may help and/or give errors when it fails.
Of course, as soon as I reported this bug, it started to work again!
I am using a hourly cron, but I was redirecting error messages to /dev/null. I'm now logging them into a file and will reply with more details if the issue happens again.
A Miracle For a Happy New Year!