After adding a plugin, like wp e-commerce and later I also tried others, on a fresh development installation I get Errors I don't have on my live server like:
Undefined property: WP_Query::$post in C:\wamp\www\wpecommerce\wp-content\plugins\wp-e-commerce\wpsc-includes\theme.functions.php on line 1025.
When I look in this file WP indeed tries to do a call on $wp_query:
'$product_id = $wp_query->post->ID;'
Does anybody knows why I get these errors on a fresh development environment while I don't have this problem on my live server?