I have several menu items in our main menu, and each of them has several sub-items. All of them display correctly EXCEPT one - this particular menu only displays the top-level menu item, unless you're actually on the page that the top-level item links to - then it displays all the dropdown sub-items.
The only difference in the non-working menu is that the sub-items link to external sites, rather than internal pages.
Here's the menu setup:
The Featured Exhibitor menu works - i.e. the dropdown displays on all pages. The Contact menu doesn't work - on all pages, all you see is the top-level Contact link. When you click that and are taken to /contact, the menu suddenly displays all the dropdown links. Because the sublinks are to external sites, there are no issues with node permissions or anything, and even if there had been, at least things would have been consistent (they wouldn't have displayed anywhere if the user didn't have access.)
Here's the menu displayed on /contact:
We've tried switching the theme to see if there was something funky about ours, but it does the same thing no matter what template we try. Any idea what would cause this?
EDITED TO ADD
When I look at the rendered source, the subitems of the contact menu are not included on pages other than /contact. So it doesn't seem to be a style issue.