2
header.php line 112:
$xoopsTpl->assign('xoops_pagetitle', $xoopsModule->getVar('name'));
two objects are called, $xoopsTpl (Smarty object for presenting final output) and $xoopsModule (object for the module you are in)
Since the preceding line is
if (isset($xoopsModule))
I think that the problem lies with the $xoopsTpl object, which isn't initialised properly. On the other hand - even earlier, we have calls to the $xoopsTpl object...
I am fumbling a bit now. From which file do you see this? Right after installation? On all pages? Can you log in? Can you go to admin area?