Problems with SWFObject in IE

I've recently installed the SWFObject plugin and it works fine on Firefox. However, whenever I try running it through IEEEEEEE (I have IE 8 and IE 6 and this problem applies to both) I get the following Javascript error when the Dialog box's OK button is pressed :-

"Line 112
Char 2
Error Object doesn't support this property or method
URL <site url>/FCKEditor/editor/fckdialog.html"

Which equates to the following line :-

112 : if ( window.frames["frmMain"].Ok && window.frames["frmMain"].Ok() )

Obviously the most direct answer to this problem is "don't use IE", but the client who uses the site most likely does, so I need to be able to resolve this.

Any chance anybody could help me because I am so far at a loss?

Many thanks,
~M