Version 8.5 comes with a custom Spell-checker that is embedded into the application. It is weird it has stopped working but you can control it thru the 'Edit' menu, there are several spell-checker options there.
I want to turn the spellchecker off - but as in other post the option is greyed out. The red lines underlining supposed errors (ie most of the html code) are very annoying! Wish I'd stayed with the previous version.