it's becoase the width of the form exceed the width available to the content area.
in the content.css file, change:
#outerWrapper #contentWrapper #content {
margin: 0 0 0 176px;
padding: 5px 20px 10px 20px;
font-size: 100%;
text-align: left;
vertical-align: top;
top: auto;
}
to:
#outerWrapper #contentWrapper #content {
margin: 0 0 0 176px;
padding: 5px 20px 10px 20px;
font-size: 100%;
text-align: left;
vertical-align: top;
top: auto;
overflow: hidden;
}