Thanks for your response. After reading it, I opened up the photosynth app after not having opened it in a few days. It appeared that I was logged in- under accounts, the 'windows live' line indicated I was logged in, and below that, it said "photosynth ACatalinaH." Then I tried to share a photo via photosynth, and I was logged out.
I then switched off wifi, and it automatically logged me back in. I was just able to successfully upload a photo.