I'm not seeing anything wrong. The problem does not occur in Opera 7, so I think it might be something to do with Opera 6. I even tried removing it from the table cell but it still does the same thing, as if it's not reading the subOffset=5 part of the code. Perhaps something Andy might have to check.
The problem is coming from the stylesheet. MARGIN-TOP: 20px; is what is causing the submenus to open directly over the main menu. I have no idea if there's a way to fix that in the menu_data.js file or not. And, I don't know why it's doing that from the style sheet. If you remove that, then you get what you see on the sample from milonic.
Ruth - PS I like your dog. Looks like mine when I was growing up.
I don't know why you didn't think of that I didn't actually think of it either, I just used your files with the sample menu and it worked, so I figure it had to be something else on your page....that kind of left the easiest to try to remove first and that was the stylesheet.
Mine wasn't a purebred, what we call heinz 57....a mixed breed but he sure looked like that picture.