jshttprequest failing when added Zend Library

Question

I have a php project in which I now need to use Zend library for uploading video on youtube

the code for uploading video on youtube works fine if it is run as a separate project.

But when I add Zend library to php project like this

require_once('Zend/Loader.php');

Zend_Loader::loadClass('Zend_Gdata_ClientLogin'); Zend_Loader::loadClass('Zend_Gdata_YouTube'); Zend_Loader::loadClass('Zend_Gdata_AuthSub');

Zend_Loader::loadClass('Zend_Gdata_App_Exception');

the jshttprequest starting throwing error on firebug it just show internal server error 500 on line 398

if I only add this line require_once('Zend/Loader.php'); no error is reported but when i try to Load classes like this

Zend_Loader::loadClass('Zend_Gdata_ClientLogin'); Zend_Loader::loadClass('Zend_Gdata_YouTube'); Zend_Loader::loadClass('Zend_Gdata_AuthSub');

Zend_Loader::loadClass('Zend_Gdata_App_Exception');

jshttprequest starts throwing error.

Video upload still works but the already existing functionality of code fails to work

any suggestions

thanks