looking here http://piwik.wecowi.de you should probably see that the charts for visitors per day and visitors per hour are not working
It looks like you installed the new release over your previous installation.
Please remove these files:
did not change anything
Seems to be working fine now.
yes, after deleting the whole installation except the config. But that's not the way to do this for every release. First deleting all files and the upload them and that all through FTP, that's an hour work.
Sorry for the inconvenience: we could/should have noted the files removed in this release.
FWIW I don't believe you needed to remove all the files -- I'm guessing the deleted files (above) and the tmp folder would have been sufficient.