Hello,
I am getting this same error (both locally as well as on the demo link that you posted) I have the same results as the other person - the first time I press the back button, the editor is cleared. If I click Back again, then I get a javascript error. (Permission denied)
The error seems to be at the following point, which seems to be in WinIE.js
var arr=Ox374[OxO79c3[0xa]][OxO79c3[0x5]].tags(OxO79c3[0x21d])
I'm Using IE 6 (or to be more specific 6.0.2900.2180)
Hopefully there is a solution to this, as it's a bit of a show-stopper from this end.
Cheers
Kane.