This morning I woke up to a surprising email from my Joomla site. It turned off Thickbox. I didn't know it could do that!

I've had absolutely no problems with Thickbox since I first installed it a month ago. (v1.2)
This error was the reason: Call to undefined method JDocumentFeed::addCustomTag()
/home/qoolery/public_html/plugins/content/mosthickbox.php : 66

I turned it back on and it worked fine. I then installed the new version, so I hope it doesn't happen again.

Thanks for your good work.

It happened again with the new version of Thickbox. I noticed that the last version fixed a conflict with Articles Anywhere. I installed Articles Anywhere four days before this started happening. Except for the latest version of Thickbox, I haven't installed anything since.

It may also be worth mentioning that I'm using Joomla v1.5.17, which was upgraded from v1.5.15 over a week ago.

This link explains the new Joomla behavior of "automatically disable plugins that trigger an error during initialisation": docs.joomla.org/Why_are_my_plugins_automatically_disabling

kawinaorg wrote:
Call to undefined method JDocumentFeed::addCustomTag()
/home/qoolery/public_html/plugins/content/mosthickbox.php : 66

Your doctype seems to be a feed (xml), so Joomla tries to add the header tags to a xml file which off course is nonsense.
It may help if you replace line 66f of /plugins/content/mosthickbox.php with this:

I've just installed the plugin. but doesn't work. but I didn't get any error.

I have other plugins installed as well[simple image gallery]. is there any chance to conflict?