I tried the following thing.
Adding die('called') after every function and check if the script breaks. First function executed, second, third and so on. Up to the end if I add die('called') the script gets executed and you get output (well doesn't look as the j1.5 backend, but at least output. That is just for your info what I did.
The problem comes as it seems from your php version.
Here is a similar one. I suppose that your xampp installation runs php5 and php4
forum.joomla.org/viewtopic.php?p=1455717
The best thing - ask your support for upgrade to php5 and if it is still not working then we will think on another solutions.