Below is the response from Telerik support team which resolved the problem.
I think the problem comes from the fact that the RadSpell control uses an IFRAME element to display the spell check dialog. The IFRAME is considered as part of the page. When you set the document domain on the page, the IFRAME ends up with a different domain and the browser refuses to allow script access to/from it. I don't think that it is possible to change the domain of the IFRAME (http://msdn.microsoft.com/en-us/library/ms533028%28VS.85%29.aspx
). The only workaround I can give you is to set the UseClassicDialogs
RadSpell property to true
. This way the spellchecker will use a normal browser window instead of an IFRAME and you should not see an "access is denied" error any longer.
<rad:RadSpell ID="RadSpell1" UseClassicDialogs="true"
runat="server" ControlToCheck="txt1" />
the Telerik team