Internal Server Error I am trying to edit fields.  When I go to Settings-&gt;Fields and then click on a field, I get a message that reads:

Internal Server Error

Craft\Model and its behaviors do not have a method or closure named "availableAssetSources".


Then I looked in the utility logs under server info, it reads:

Level:  error
Category:   exception.Twig_Error_Runtime
Message:    exception 'CException' with message 'Craft\Model and its behaviors do not have a method or closure named "availableAssetSources".' in /home/christen/6989-CLG-Web/craft/app/framework/base/CComponent.php:266


I am including the code written on line 266, in case it helps:

throw new CException(Yii::t('yii','{class} and its behaviors do not have a method or closure named "{name}".',


What does all of this mean and how can I fix it?

Thank you so much!
You're running Craft 2.6+ and you've got an older version of the Redactor I plugin installed that isn't Craft 2.6 compatible.  If you download the latest version of the plugin and install it, the error will go away and Redactor I will work as usual.