We love SeeFusion - its been a life safer in helping isolate slow running pages and queries.
But when CPU/Memory is totally pegged on the server its Flex interface may not load. As an alternative you can load it's HTML only interface which gives you a chance to spot the offending page/query.
To do this add /html to the SeeFusion URL. E.g instead of http://machine:8999, use http://machine:8999/html.
You can also kill a process from this page, but when it does that it'll redirect you back to the Flex interface. If it's still not loading, just go back manually to the HTML page to see if the process has been killed.
When killing processes with SeeFusion, you may need to do it a few times. The first attempts will try to do it gracefully, whereas subsequent attempts will try a hard kill.