Typing (or cutting and pasting a URL) into AB does work but you have to include the full URL. Spot the difference here:
www.google.co.uk is non-clickable but
http://www.google.co.uk is clickable.
It's the http bit that makes the difference.
As Boo has indicated, the changes were explained in the editor's blog back in June. AB used to have a 'rich text editor' (for providing bold type, clours, etc) which used a form of JavaScript that presented security issues for your PC. The designers of decent web browsers recognised the security risks and refused to implement this form of JavaScript in their browsers. (So, for example, people using Firefox, never had the ability to use bold text or colours). Belatedly, Microsoft realised the problem and brought Internet Explorer into line. (IE7 does not support this form of JavaScript. So, anyone buying a new PC, or simply updating Internet Explorer to version 7, would find that they couldn't use the rich text editor).
Since many AB members already couldn't use the rich text editor (because we use Firefox) and eventually nobody would be able to do so, this facility was removed.
For a more detailed explanation, go the editor's blog and change the date (at the top right-hand corner) to June 2006.
Chris