Hi Gents,
Looks like we have a little problem with some scripts on the server-side of the update system. I also have noticed some issues like the ones you're experiencing. As Yuriy says, it's a mater of trying several times. A few tries with Resources > Updates > Check for Updates and the system will accept your user name and password (please be careful when copying/pasting your password, not to include any whitespace at both ends).
I'll try to fix this issue as soon as possible. Anyway, today we'll upload new installation packages for version 1.7.0.697, so you can download the full package and reinstall. Then you'll have build 697 installed and only the script and documentation updates will be available for you.