Do you have "Show subsites" checked on your site  Settings->Navigation page
in the parent site?

No but if I do enable it then all of the sites  in the top  navigation appear
twice.

I had to give someone with no SharePoint training admin rights. He said things
have been weird after making a change several months ago. I asked him what he
did, and why he didn't tell me sooner. Well you know how that went over.

Check in the Global Navigation section under the Navigation link and make
sure that he didn't add  manual links for all the existing sites  because they
weren't showing up with Show Sites turned off. If he did then turn on Show
Sites and delete the manually created links.

Yeah, just delete all those manually-added site  entries and then flip the
Show Subsites switch.

It appears that was this problem. He disabled the show sites  and created
headings.