5.5 to 6.1 upgrade problems

I have just upgraded from 5.5 to 6.1, and am experiencing the following issues:

  1. I am logged is as administrator. When I click on “Settings”, I get a page with only “User ‘anonymous’ doesn’t exist.” Why do I need an anonymous user, and how do I create one?

  2. graphs are not being generated. Graph returning visits and Last visits graph display: "Open Flash Chart
    JSON Parse Error [Syntax error]
    Error at character 0, line 1:

0: Preparing archive: skipped, archive is before the website was created"

  1. all widgets display “Preparing archive: archive already processed [id = 48]…” at the top. The number changes depending on the day.

  2. visits overview is showing broken images.

How do I fix these issues, particularly since I cannot even change the settings?

Solved:

forum.piwik.org/index.php?showtopic=8961
forum.piwik.org/index.php?showtopic=8861