Call to undefined method _rebuildTree()

Cleaning up test installation.
Deleted a number of categories.
Then changed the parent category for one of the remaining categories.
Got this error.

Fatal error: Call to undefined method hikashopCategoryClass::_rebuildTree() in /.../user/htdocs/administrator/components/com_hikashop/classes/category.php on line 430

Hikashop 1.4.1
Joomla 1.6
PHP 5.2

Thanks for the bug report. The fix is easy: just remove the _ of that method name as the method name is rebuildTree and not _rebuildTree.

That will be fixed in next version.