Modx not accepting new data

Modx has been working fine previously, however I have had problems lately getting it to accept new data.

The only thing I have changed was something to do with a config file permissions because I got a warning from the modx dashboard that a file still exists and another was still writable.

I tried to add GoogleSiteMap plugin to my site. I get the error "This XML file does not appear to have any style information associated with it. The document tree is shown below." and error log [2012-08-25 07:29:17] (ERROR @ /index.php) Could not retrieve data to cache for resource 35

I tried looked at the files for the plugin and some werent set to 755, so I tried to manually set them to 755 to no avail. So I ssh chown to my ftp username and set the files to 755.

I still get no data from the xml file, so I decided to move on.

I tried to create a symlink document and it gave a message of saved. However, if I tried to click on that document to see the settings, the manager would give the detail side as a blank page and the document list would refresh and show the element list. Wasnt working so I moved on.

I tried to create a regular document, with a regular template that works with current pages on my site. It gave me a saved message, but if I click the preview button to see the file, it shows the correct url but defaults back to the main page (like document not fount).

from the error log [error] [client PHP Catchable fatal error: Argument 1 passed to xPDOObject::load() must be an instance of xPDO, instance of modX given in /var/www/vhosts/httpdocs/core/xpdo/om/xpdoobject.class.php on line 404, referer: /manager/?a=66
[Sun Aug 26 11:08:50 2012] [error]


MODX Revolution 2.2.4-pl (traditional)
php 5
mysql

Did you happen to change anything in permissions and/or user context access lately?

Did you try clearing the core->cache files?