It looks like your server has upgraded to PHP4 - where the <?php_track_vars?> directive has been depreciated.
With any luck your host has set track_vars = 1 in their php.ini file. If not, then you're stuck AFAIK. Which is the annoying thing about the depreciation of <?php_track_vars?>
If your host HAS set track_vars = 0 (which I think you can tell with phpinfo()😉 then you just need to remove the <?php_track_vars?> directives from the top of your scripts and they should work okay.
You might want to test them again, just to make sure they work under PHP4. I had to make some minor mods.. but most of that was due to my host neglecting to include the calander functions in their PHP4 install.. which was a pain because I was using them.
/Mike