[eluser]SneakyDave[/eluser]
FYI, I started getting this error trying to port a CI PHP4 application to PHP5. All that was changed in the code was changing the views from using the PHP short tags (<?) to the more recommended full tags (<?php) because short tag support was turned off on the PHP5 installation.
It might have something to do with the controllers constructor method, since it works different between PHP4 and PHP5? I don't know. If I find something out, I'll post about it.