404 Error Pages Do Not Display Custom Navigation Menus

[bozzmedia]

When calling wp_nav_menu on a 404 page (404.php) no menus are displayed. There may be a potential conflict with numbers in URLs.

This is resolved when permalinks are set to
/%category%/%postname%/

Please see: ​http://wordpress.org/support/topic/custom-menu-not-displaying-on-404-error-page

This sounds like a plugin conflict to me, Probably something hooking into the pre_get_posts filter and modifying all Requests (including the one that builds the menu).

Can verify this on a Clean install of 3.3 running one of the default themes with no plugins?

Good point. I tried it with clean Twenty Eleven and could not replicate this.

Have you heard of this 4-digit permalink issue before or what it may be a symptom of? If you visit www.yourdomain.com/111 no custom menu is displayed but www.yourdomain.com/1111 it is. Thanks!

Have you heard of this 4-digit permalink issue before or what it may be a symptom of? If you visit www.yourdomain.com/111 no custom menu is displayed but www.yourdomain.com/1111 it is.

/123 will be page 123, /1234 will be year 1234 if using /%year%....%postname%/ permastructs, which would explain why /%category%... works for you.

If there's a plugin which is altering year archives or something, that would cause it.