problem to register error -not possible to fomplate

[avitor]

this error i have when i try to register to forums
tha page of register is shows ok
when press on complate register is shows this error

Fatal error: Cannot instantiate non-existent class: simplexmlelement in /home/content/a/v/i/aviturpiya/html/muleforums/includes/functions_vbsfs.php on line 45

i disable the plagin from vbulletin optins=and complate register works ok
but ? is not shows home page anymore

and gote this eroor

Fatal error: Call to undefined function: print_portal_output() in /home/content/a/v/i/aviturpiya/html/index.php on line 47

and not possible to log to home page

i try whet to put this - define('DISABLE_HOOKS', true); in place you wright me

and not helps

--------------- Added [DATE]1210365140[/DATE] at [TIME]1210365140[/TIME] ---------------

please i nead help
my site is close cose not posibble register

[Marco van Herwaarden]

To troubleshoot this, please remove any hacks and disable your plugins, then see if you still have this problem.
Note: To temporarily disable the plugin system, edit config.php and add this line right under <?php

define('DISABLE_HOOKS', true);

If so, reupload all the original vB non-image files (except install.php). Make sure you upload these in ASCII format and overwrite the ones on the server.

If your problem still exists, please create a new Style with no Parent set. Now browse the forum using this new style, do you still have the same problems? If you are troubleshooting login or guest issues, you will need to set this style as board default in the vBulletin Options.