Thanks a lot for your suggestions. It's all different in the meantime - I don't know what started it, but all of a sudden, while working in the admin panel, the password protection started to work - which means, I couldn't access any of the admin's functions (not even viewing the site or logout) without being asked to enter my password. But: my password was not accepted (nor one of the others I stored in .htaccess. Some minutes before, all my permalinks broke down... so that's a bit of a mess! I will have to check this out again by uploading a new .htaccess, I suppose. I am busy at the moment but will be back later - in the meantime many thanks again for your taking care!
PS. macmanx, I didn't save the password in my keychain.