Warning: explode() expects parameter 2 to be string, array given in menu_attributes_preprocess_menu_link() (line 340 of menu_attributes.module).

+++ b/menu_attributes.module
@@ -337,7 +337,7 @@ function menu_attributes_preprocess_menu_link(&$variables) {
-          $value = explode(' ', $value);
+          $value = is_array($value) ? $value : explode(' ', $value);

That's backwards but I get your gist;) Also, I'd actually consider to throw a watchdog error here because you have some other rogue module sending your classes in non-array format which is not part of the API. I know I've fixed this in other modules before...

@tom friedhof Oh it's not backwards, I just have it backwards in my head... I usually do !is_array() ? ACTION : DEFAULT... not to worry there.

I'm just a bit curious why nobody has brought this up before? And how did it get to be not a string in the first place? I know drupal_attributes() expects an array for the class attribute.

@tom friedhof I'm going to commit this, but if you could tell me how it got in there as a string to begin with it would really help.

Well it should expect an array as that's how Drupal's attribute APIs work. I'm guessing on the other end we aren't usually serializing the attributes with that in mind. Strange indeed. Oh well thanks again for the patch and the bug report.