I’m having the same issue. The only problem is that since I’ve set up my WP.com account, I’ve changed the URL of my private WP install, and so I’m now just getting a redirect to my 404. I have no way to change to the new URL style, or check stats for my site. ??
In addition, I’m using the WordPress.com stats plugin, and this is causing the dashboard on my private site to fail (once the module loads for the stats preview, it seems to pull my 404 into the whole page, then redirects to a blank white page with a smiley).