False 'mobile' positive on Windows 7 / IE 8

Hey everybody.

I got a laptop with Win 7 / IE8, when i visit a site with the back to top button, it does not render the button at all. JS isnt loaded. So i commented out this:

<?php
  if (variable_get('back_to_top_prevent_on_mobile', 'TRUE') && (is_mobile())) {
//    return FALSE;
  }
?>

Now its working fine again.

The output for my useragent:
Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 6.1; WOW64; Trident/4.0; SLCC2; .NET CLR 2.0.50727; .NET CLR 3.5.30729; .NET CLR 3.0.30729; Media Center PC 6.0; OfficeLiveConnector.1.3; OfficeLivePatch.0.0; MAAU)

Thnx for this great module! (and because its on the front page, should i test http://drupal.org/project/scroll_to_top ? See if that fixes it?)