Code:
 #productAttributes .clearBoth {display: none;}
The above CSS doesn't work because it removes all .clearBoth from other elements within the attribute display area resulting in very funky layout.

However I got the desired horizontal affect. See Nahid Fashions' Signature Chic I

I created an override copy of /includes/modules/attributes.php in my template directory.
I then changed all (7) the occurrances of

Code:
$tmp_attributes_image .= '<br class="clearBoth" />' . "\n";
to

Code:
$tmp_attributes_image . "\n";
That seems to have worked and only affects the attribute images.