I see in quite a few threads that members can't use their spell check. I'm the worst speller so I needed to find a solution in the trial phase and I did.
Try that and if it's now working for you (other browsers work the same way) post here and I'll try and help find your solution.
Because we use a fully WYSIWYG (What you See is What You Get) editor, the right click is needed to be able to pull up image and table properties, cut and paste, etc. However, fear not. There is a work-around to be able to keep using it.
If you hold ctrl (PC) or Command (Mac) when you right click in Firefox, it will treat the right click as though it's outside of the text editor.
This is an extra step for folks, but the idea was to provide the power of the context sensitive menus in the editor (to align images, add borders, color table cells, etc.) but also enable you to take advantage of Firefox's spell check.
Try that and if it's now working for you (other browsers work the same way) post here and I'll try and help find your solution.