I have the issue with Chrome in Win7, it happens only some times that i am writing and all the red dots disappear from sudden and i must write random text or delete text to make the spell check work again.
It usually happens when I enter some smilie / image / paste text in the editor. I'm not sure if this is chrome related, it happens in the 1.1 editor and 1.2, but it is frustrating to make the spell checker work again when it happens.