thumbnails contain no images

i have installed a premium theme on my website but the problem is that no images are shown in the post thumbnails it only stays white box,even though i use same rss feeds on my other website http://www.todayheads.com and all posts that contain images have a thumbnail post but in my new website http://www.topicsland.com no images are found in the 1st site i use wp 3.3 in the new one i use 3.3.1,plz help me????