Currently the menu separator image in getMenu() is the horizontal line image. To allow greater flexibility for theme designers, this can be changed to an empty <div class="HR"> as it is in getMenuAsList(). This will not break any existing themes, but the separator will not show up unless the class is added to CSS.
The current line is in a DIV with the menu ID and other attributes but I'm not sure they are necessary.
This is around line 205 of class_menu.php.
Veit - was this part of your recent changes?
I only changed the behavour for getMenuAsList() to use an <li class="separator">.
I will check to do the same for the classic menu, means <div class="separator">. Difficulty will be not to have an empty div which can cause display problems.
This must be postponed, because I could not get it working with IE6 and IE7. Alle other browsers (IE8, FF3, GC, Safari4 and Opera) work fine. I also tried with a span tag between, but didn't help.
At least I have moved the inline styles to the theme css and you can deal with them.
If you have an idea to get it working with css also for these browsers I would like to implement it.