If you cant change your signature, this is because you have the WYSIWIG editor enabled on your profile. Since our skin isnt fully upgraded, that it is causing an error.

You will be relieved to know that it is a simple fix. To change your view from the WYSIWIG editor to the classic view, do the following
profile ->options -> change message editor interface from "Show Enhanced (WYSIWYG) Editor Toolbar" to "Show Standard Editor Toolbar"