editor.php on line 309 customer add/edit product

I am receiving this error with Marvikshop 1.0 beta4 on Joomla 1.5.20 where this Notice and Warning are appearing in the Products List when I go in to edit or create a new item to be added to the cart.

Warning: Attempt to assign property of non-object in /home/globalte/public_html/libraries/joomla/html/editor.php on line 309

I already have TinyMCE 2.0 defaulted in the global configuration and my admin user account is using JCE 1.5.20 and as this is not an issue with the editors it must be something to do with VirtueMart as this is the only place I am experiencing this particular issue. Any ideas?

[Solution found for similar problem]

Same error msg's here, but ONLY on the 'Edit Store' page.
page displayed the Store fields, but in 'bare' layout, e.g. no Save/Apply/Cancel button, description box could not be seen etc.

however, in joomla 'global configuration/site settings', my 'Default WYSIWYG Editor' was blank (nothing selected, also the dropdown box didn't show anything).
so I activated in joomla 'PlugIn Manager' the 'Editor - TinyMCE 2.0'.
then I selected it in 'global configuration/site settings'.

now, I'm still getting the errors, but the rest of the page looks ok (including save button), so I can do the changes and save it at least.

PHP Warning: Attempt to assign property of non-object in C:\Program Files\wamp\www\mywebsite\libraries\joomla\html\editor.php on line 309

PHP Fatal error: Call to a member function get() on a non-object in C:\Program Files\wamp\www\mywebsite\plugins\editors\tinymce.php on line 57

Note that the last error (line 57) has disappeared since I did the editor changes as described above.

Then, I repeated above, and also enabled the 'Editor - NoEditor' via the Plugin Manager.
(still default editor in global configuration is TinyMCE)
Now, all errors are gone!

Note: I didn't set any specific editor for the user (administrator) via Site/User Manager (Parameters/User Editor). You might want todo this aswell if above doesn't fix your problem (you should be able to select one of the 2 available editors now).

Hope this helps a bit!