Can you paste the whole debug info, not just one tiny fraction of what is needed to make sense of things?
Although if I had to hazard a guess -- you didn't update your plugins, and they are still trying to use the old code. Pretty much every plugin has been
ported over.
Start calibre via the command prompt, using the command
Code:
calibre --ignore-plugins
and see if it works. Then update your plugins, and restart normally.