I had an issue where blocks of text were displaying in one order in the preview, then sending in another. After talking to Marketo Support, it turned out that if some of your elements are vertically-aligned (e.g. "vertical-align: top") and others aren't, the vertically-aligned ones will default above the others, regardless of actual order.
Not sure if that's your problem or not, but I figured I'd throw it out there.
Adchoices