I just signed up and am having the same problem as topic starter.
Once I filled out the form and pressed OK I was sent to a page telling me to look in my e-mail but the page was all HTML source.
I thought nothing of it but after confirming my signup and trying to login the wordpress.com secure site keeps redirecting me in a loop and Firefox cuts it off. You guys working on the servers or something?
Maybe unrelated but still; I can logout of this forum but on the main wp.com page I show up still logged in.