I'm able to log in with my Windows Live ID without problem, and I can see my three existing photosynths, but I'm unable to create a new photosynth.
When I click "create" the system takes me to this page http://photosynth.net/create.aspx , which prompts me to "sign in" (I already AM signed in!) or "Download Photosynth" (it's already installed, and I've uninstalled and reinstalled just to be certain).
This behavior happens consistently with all browsers (I've tried IE 9, an old version of Firefox, and Chrome).
Thanks in advance for your help.