If the view-grid has an attribute containing class, the class is property is printed twice, as in the following HTML excerpt:
<table class="views-view-grid cols-3" class="views-view-grid">
The code responsible for this is in views/theme/theme.inc and views/theme/views-view-grid.tpl.php.
views/theme/theme.inc, line 761:
$vars['class'] = 'views-view-grid cols-' . $columns;
views/theme/views-view-grid.tpl.php, line 16:
<table class="<?php print $class;
I am guessing there should be a check as to whether the
$attributes string contains class, in which case the
$class string should not be printed beforehand.