I recently upgraded to 2.6.1 and after fixing the first issue upgrading brought to light I am now at the next one: the analytics dashboard doesn’t show some of the data. All requersts except for the Live and UserCountryMap fail with an error 500 witht he following reason: “ViewDataTable ID ‘tableAllColumns’ is already in use!”. This applies for all three “websites” running on that piwik instance. You can see it in action on http://stats.getnightingale.com. Interestingly the API, or parts of it seem to work fine, as http://dashboard.getnighitngale.com still displays visitor data.
Edit: I manuially reuploaded the 2.6.1 files and now it’s fixed, I guess there were multiple damaged files from the auto upgrade.