For the attention of those running their php with: short_open_tag = Off
Just in case anyone else rans into this: I've just upgraded domain mapping plugin from 3.0.5 to 3.0.6 and noticed that I had a load of PHP code in the new "Settings -> Domain Mapping" tab.
The fix is to edit domain-mapping.php at line 386 and make sure that the php open tag used is "<?php", not "<?".
Hope it help.