changedata.php

[vions]

i've been having a headache for the past few hours. my template (phantom, converted from html5) was working fine. then, a problem arose. i kept on getting a message of "oops! page not found" (with a reference to changedata.php showed up on url - see attachment) each time i tried to edit or create a page with image or table in it. any ideas on solving this problem?

edit: i tried to change the template into cardinal or innovation, to no avail. any help? thank you. is this similar to the on on this thread, http://get-simple.info/forums/showthread.php?tid=4677?