Thumbnail images not showing

HI I’ve installed the WiseBusiness theme on WordPress 3.0.1 which uses the Simple Post Thumbnails plugin. I have activated the plugin and uploaded a thumbnail to the posts and made sure the /wp-content/thumbnail folder is writable but the thumbnail images are still not showing on the homepage I am working on . For troubleshooting purposes I’ve tried reinstalling wp and the theme files to a testing site from scratch and the thumbnails are now there but the links appear to be broken. Also, the sidebar/footer is broken on the other pages https://109.123.85.12/~quantums/?page_id=21 (not sure if that might have something to do with it?? I though someone with a better knowledge of wp than me might see a simple solution without necessarily knowing the theme I’ve used. Could anyone suggest why this might be happening and how I could fix it? Thanks