jquery wysiwyg throws "Object doesn't support this property or method" on postback.

Answer 1

It looks like IE doesn't support contentWindow.document - I think that code needs to be something like..

return

element.contentWindow ?
element.contentWindow.document :
ownerDocument

Answer 2

Do you see the bit of code that is commented out in the wysiwyg plugin. Re-enable that bit of code and take out the return statement above it. That code implements the browser-aware bit that will make the code work in IE.