Error: Undefined index: semantic_field_instance_format in semantic_fields_preprocess_field() (line 153 in .module)

Notice: Undefined index: semantic_field_instance_format in semantic_fields_preprocess_field() (line 153 of /www/htdocs/*myroot*/sites/all/modules/semantic_fields/semantic_fields.module).

Is caused by certain funny behaviour of php5. PHP 5.x register_globals is being handled a little differently than with 4.x f.e. and it generally prefers a variable to have been initialized before use, or before ask anything.

A work-a-round would be:

// ++ add this code at line 153
else if (isset($instance['semantic_field_instance_format'])) {
  if ($instance['semantic_field_instance_format'] == 'default' && $field['semantic_field_format'] == 'default') {
    $use_defaults = TRUE;
	}
}

instead of

// -- remove this code at line 153
else if ($instance['semantic_field_instance_format'] == 'default' && $field['semantic_field_format'] == 'default') {
    $use_defaults = TRUE;
	}
}