After calling execCommand('unselect' false, NULL) on a desigMode iframe, all subsequent call to getRangeAt() or createRange() will result in a script faliuer. in this case rangeCount is eual to 0, after a failed createRange(), getRangeAt() or alert() every thing will be working again.
Making a selection will also solve the issue.
A test case would be very helpful to demonstrate the issue here.
Created attachment 18151 [details]
test case (doesn't fail)
I have tried to make a test case, but couldn't get it to fail. We won't be able to do much with this bug without more information.
(In reply to comment #3)
> Created an attachment (id=18151) 
> test case (doesn't fail)
> I have tried to make a test case, but couldn't get it to fail. We won't be able
> to do much with this bug without more information.
Anders, after many months without providing more details regarding this issue I have to close the report. Feel free to reopen it if you provide more details.
I currently have a work around in place and won't have time to deal with it for a long time so closing it is fine.