1. be patient. there are a LOT of tags. it may take a few seconds or so. wait for it to finish loading.
2. shift+click on links and they will open in a new window for you. (if not, you will have to press back in your browser and wait for the tag cloud to generate all over again.)
3. generate your own tag cloud for your tumblr. http://rive.rs/projects/tumblr-tag-clouds
the tag cloud should appear below in a few seconds. if it takes longer than a minute or two you might want to try refreshing the page.