Bizarre...I just tried that same demo...clicked the link for 'Check Spelling' from the edit record that was already opened on page load. I get a script error:
Line: 7
Character: 2649
Error: Object required
Code: 0
I am running Vista SP1 and I get that same error with my code. if I click 'Edit' on another record, the script error is still there, but it works. It seems like something isn't initialized correctly on page load.