Problem appears in Microsoft CRM 4.0.

Hi,
I used a plugin to set the state of an entity in Microsoft CRM 4.0, when this error message has appeared (see below image):

Honestly, I am kind of confuse of the error message. I don't have any idea what it means.
Any advice for me on what I should do?
Thanks in
advance.
Microsoft Dynamics CRM — Webpage Dialog
