Theme::header()is now an undefined function in line 15 of header.php I guess there must be something new that I'm not aware of. I didn't have time recently to follow all threads in the dev-group.
I think I would be safer that I always use the default theme and may be just a customized sidebar. I'll have to find time even for a simple task like that.
[edited] my custom K2 is back on but with my custom theme functions removed.
Theme::header()is now called by