There's a setting in your profile under Look and Layout titled Show WYSIWYG editor on post page by default, it's been known to cause problems both unchecked and checked(default), I unchecked it, see if that helps, you can always check it and save the settings if it doesn't work or causes other issue by being unchecked. The spell check is a pop-up, if you have a pop-up blocker, it may prevent it from showing which may be an entirely different issue to deal with, you should be able to specifically allow pop-ups on GBO in your browser.
Tim
