"category not found" when I click next page on some threads

The spell checker was working, but now even thought it is high lighted it doesn't seem to work.

It works in my browser just fine, right now - Latest google Chrome browser. ( which is the browser that we recommend for our site here) 

The actual spell-checking is a browser function; it's not implemented internally by our post editor - so if it's not working when you have it highlighted, then it's something in your browser setting that is shut off, or maybe just glitching. Which web browser are you using?