Hi there, just a quick note about how to stop the nightmare of Joomla 1.6 lack of debugging output. First, you should install  Firebug for Joomla 1.6 plugin : now you can use fb() function to log variables directly in the Firefox firebug panel. Another nice trick I use is to put a vardie() function at the top of index.php, the function looks like this:
function vardie($var){
This (and other useful functions) can also be placed in a file called defines.php in the main folder, this file will not be overwritten on upgrades and it is automatically parsed at start. df()is just a fake function to trigger a stack trace if you have xdebug installed (which is another must-have PHP tool). Last but not least, Joomla uses an evil try/cacth block at the to of the application dispatcher, this makes 500 error messages completely unuseful. To fix this, you can change around line 196 in includes/application.php
// Mop up any uncaught exceptions.
catch (Exception $e)
    // ABP: get a decent stack trace
    $code = $e->getCode();
    JError::raiseError($code ? $code : 500, $e->getMessage());

this way, Joomla will dump the exception with the stack trace (remember? xdebug). These tricks will make your debugging experience *much* easier.