Kathy, You can try safari, I might have mentioned that before, but I can't remember ,so it did not work in safe boot. That really starts to make me think that there is an OS issue, as safe boot disables all 3rd party software, and only allows native software to run. We use it for diagnostics to help find issues. There are a couple of more things that I would like to try before I give you a suggestion. Also does your Adobe function? Are there issues with any of your other software? You can let me know on the next communiqué. You can also try Word and/or Pages. Purposely spell some words wrong not so wrong that it could never figure them out, but a letter or 2. Try the following in all the applications mentioned in this post: Finish typing, just a few lines in each application, one application at a time then close that application, and try a new one. In each one after you (don't forget a misspelling) go to edit>spelling and grammar and click show spelling and grammar from the sub menu, or check document now, see if it finds the misspelled word and try to correct (replace)it then click find next and see if it will go thru the whole doc and fix it. Get back to me and we will try one more diagnostic test, ( I'm running out, as we've done all but this one coming up ;)after i hear back from you on the results of the tests on this page. Thank you for patience, as this has been one of the most bizarre issues I've come across. SJP