Hah, I just found the explanation: you're in privacy/incognito mode. Looks like a bug in Firefox prevents it from working properly in that mode. :/
Are the problems gone for both of you? (Either because you exited private mode; or because the timeout on the new configuration expired)
Hi David
The problem is gone for now. Everything is normal again. I'm in private mode now and had to activate cookies.
OK, good. I'll keep it as-is then until we find a better approach. Thanks for the reports!