Full message:
warning: call_user_func_array() expects parameter 1 to be a valid callback, function 'theme_block' not found or invalid function name in (drupal)/includes/theme.inc on line 656.

Switching to Garland makes the error go away.

This seems to somehow relate to having another module installed which defined a "theme override" function for blocks. In my case it's LS Block Titles from LS Extras - http://drupal.org/project/ls_extras - but my guess is it would happen with any other module that does something like:

// Hook my function into theme processing.
function my_module_theme($existing, $type, $theme, $path) {
  $ret['block']['preprocess functions'][0] = 'my_module_preprocess';
  return $ret;
}

I guess all you need is to include a dummy theme_block() function - I confirmed that adding one makes the error message go away, but I don't generally write themes, so maybe theres more to it than that?

Comments

Status:Active» Fixed

a dummy block.tpl.php did the job. I guess all themes without block.tpl.php will have the same problem

committing default block.tpl.php template from system module to the dev version. won't do any harm, so I am fine with it.

Status:Fixed» Closed (fixed)

Automatically closed -- issue fixed for 2 weeks with no activity.