Cannot fill in new thread/reply form using Firefox

[MeNeedHelp]

When using Firefox, I cannot fill in the main message box in the new thread or reply forms.
Whenever the form loads up I cannot click on the main box in order to fill in some text. I can only insert text into the title box.

The error that appears in the error console is:

Error: [Exception... "Component returned failure code: 0x80004003 (NS_ERROR_INVALID_POINTER) [nsIDOMNSHTMLDocument.queryCommandState]" nsresult: "0x80004003 (NS_ERROR_INVALID_POINTER)"

This stems from the clientscript/vbulletin_textedit.js file.

Any help is much appreciated.

Update:
This only happens when using the WYSIWYG editor and the form focus then seems to be stuck on the 'Align left' button.