Cocoa Madness!

Can anyone tell me why my menu separators in my program show up blank instead of with the horizonal line that other applications have? This only happens in the dock menu. I’ve tried adding the separator through Interface Builder and through code (with [dockMenu addItem:[NSMenuItem separatorItem]];

In the example below, my menu is on the right. There should be separators below the ~08. item and below the Stop item. They should look just like the one below the Mute item and just like the ones on the menu on the left, from iTunes.