Hiya,
The problem is being caused by the 'common.reset.css' in your includes/styles folder. This is a generic CSS stylesheet which is designed to reset all borders, margins etc. to zero for body, paragraph, div, table, form elements etc across all platforms and browsers. This is fine for modern browsers, but screws up older (and apparently some fairly modern) browser css. It is causing the margins created by the form builder to be set to zero, and consequently - in some browsers - you will get the 'collapse' you are seeing.
To test this, in your <head> section, replace:
<link href="../_includes/styles/screen.css" rel="stylesheet" type="text/css" />
with
<link href="../_includes/styles/p7csslm01.css" rel="stylesheet" type="text/css" />
<link href="../_includes/styles/p7PMMh13.css" rel="stylesheet" type="text/css" />
<link href="../_includes/styles/screen.layout.css" rel="stylesheet" type="text/css" />
(The 'screen.css' merely imports those three stylesheets plus the 'common.reset.css').
There are various common reset css files out there* in the www, all of them slightly different. I don't think you need one in this case.
Try the above and retest your site as before. Let us know how you get on.
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* a-killer-collection-of-global-css-reset-styles/
Also see: 'Is your CSS reset doing more harm than good?' [ create-custom-css-reset ]