With the UC Attributes module enabled, you receive the following error for any product node that has an attribute:
recoverable fatal error: Object of class stdClass could not be converted to string in /xxxxx/sites/all/themes/omega/template.php on line 233.
This is due to the use of
$vars['node_attributes'] = $vars['node']->attributes; in preprocess-node.inc.
I'm not sure why you have a check against that, as its pretty much always not set, except in this situation. What happens is that an object of the attributes is added to your $vars['node_attributes'] array, and when you implode the array, it throws out that error. The solution I came up with is to remove the check and simply set $node_attributes to an array. Patch attached for that fix.