Welcome to the Mesh - or at least, very close to it :)
I am going to assume that when you say "already logged in" you mean already logged in to Live Mesh and not just your computer.
I'd try to clear your browser cookies and cache (if you're feeling adventurous you can try and filter out just those related to live.com and mesh.com in an effort to preserve your other data) and then try again.
If that doesn't help then I'd suggest submitting a bug by doing the following (from the post on the forum front page):
1. Click Start.
2. Select All Programs and look for the Live Mesh folder.
3. Click Collect Live Mesh Logs.
4. Your logs will be bundled together in a cab file now located on your desktop.5. Send the CAB file on your desktop to
lmprev@microsoft.com, they'll look at it and open a bug for you
6. In addition you can ask lmprev for "Connect" access to lodge a proper bug yourself
Good Luck!
