Just a quick update;
Coinciding with the phasing out of the SHA-1 (secure hashing algorithm), operating systems and web browsers which do not support at least SHA-2 will no longer be able to use Zenbu (specifically, to access the secure pages of our website such as logging in / buying credit).
Note: This change was made on Tuesday the 4th November, 2014.
SHA-1 has been deprecated since 2011 and is soon to be treated as insecure by common browsers (For example:
You can check whether the version of your operating system and / or web browser meets the minimum requirements here;
One of the more common platforms that people may still be using (but will no longer work with Zenbu) are versions of Windows XP prior to Service Pack 3.
Arguably, if your computer is using a version of Windows XP prior to Service Pack 3, then irrespective of Zenbu, it should not really be connecting to the internet at all (for your own security / safety).
The Zenbu Team