I've just emailed my programmer to see if he can fix it. I didn't make a single change that would have done this.
So... here's a temporary fix. If you click here, it will take you to the Samples Page.Look to the far left: all the categories are listed there (and on every page but the home page). From that page, you can navigate to any other section of the website.
Hopefully, this will be fixed lickety split. Like before I wake up tomorrow. The one good thing? I just got a wake up call that I haven't backed up the site since late July. Guess what I'm doing the minute this is back to normal?