Which version of PHP are you using?
I suspect that the problem you are having is the result of the DOM XML extension not being installed on your instance of PHP on DreamHost.
You can view the output of phpinfo() to see the details, but a look at the PHP Manual DOM XML information states:
" Note: This extension has been moved to the » PECL repository and is no longer bundled with PHP as of PHP 5.0.0.
Note: This extension is no longer marked experimental. It will, however, never be released with PHP 5, and will only be distributed with PHP 4. If you need DOM XML support with PHP 5 you can use the DOM extension. This domxml extension is not compatible with the DOM extension. "
You might want to try to reset your domain to work with PHP4, and see if it works in that environment. To do this, In the Control Panel -> Domains -> Manage Domains screen, click the "Edit" link under the "Web Hosting" column of the row for your domain, and reset the appropriate Radio Buttons to select PHP4.4.x instead of PHP 5.2.x, and submit the form.
If you feel capable, you can also install your own copy of PHP for use on DreamHost and install whatever extensions you desire.
While there are not specific instruction for installing that particular PECL extension, there are some examples of installing PECL extensions in the DH WIki which might be helpful to you as examples.