Thanks but in this post does not mention the inability to access the visual editor...
You're jumping ahead. ;) Visual Editor problems are frequently the result of Javascript issues. The master list contains information on how to debug those.
If you want to leap ahead try
- Switching to the Twenty Twelve theme
- Deactivating all of your plugins (no exceptions)
- flushing your browser cache and cookies. Don't skip this step after doing the other two.
If that gets back the Visual Editor then reactivate our plugins one at a time and then theme last. That may help you find where the problem is.