Appears that Internet Explorer decided it doesn't want to open my class databases anymore. May take some time to pin down the issue, so the calcs won't work in IE for a little while. Sorry for the inconvenience. =(

UPDATE: WOW IE. As I thought, it had to do with IE not liking xml files generated with php and still having the php file type. Had to redirect a fake .xml to the file instead... Whatever, it works now. Thanks to 009MG for pointing it out.