Can someone help me.

I'm try to use Accordion Control from AJAX Control Toolkit but I have problem in Design time .... it is working fine when I run the application but in Design time I'm getting this error:

Error Creating Control - MyAccordion 'Panes' could not be initialized. Details: 'Panes' could not be added to the collection. Details: Object does not match target type.

If someone knows how I can fix this error please tell me ...

Thanks in advance.

/Todor