When user language isn't English, English pages won't show up?

I just created a multilingual Drupal 6 site, but have discovered that if I assign a user a language other than English, they don't have access any longer to the English page.

The list of languages shown as a block at the footer of http://cms.iuf.org shows different kinds of links for the different languages, which might explain the problem.

For example, the link to French is http://cms.iuf.org/?q=fr and the one to German is http://cms.iuf.org/?q=de, but the one to English is http://cms.iuf.org/ A user who is assigned a language like Spanish can access the French and German pages by clicking on those links. But the link to the English page doesn't work.

If I try to connect to http://cms.iuf.org/?q=en after logging in a non-English user, I get a Page not found error message.

I've tried all the variations I can think of when configuring Languages. The option I've had to go with is "Path prefix with language fallback" -- nothing else works.

Not sure what to do on the Multilingual system page.

Thanks for your help!

Eric Lee