Tranx,
current affairs always causes concern for OASC. It takes up a small portion of the interview but takes a lot to prepare for. Reading the Economist is a good start; it gives a brief summary of domestic and international affairs in the first few pages and more in depth articles throughout. It is usually a good idea to pick a story from each continent and three or four domestic issues and research the background of those and follow them through to the day of your interview. Try to avoid the obvious areas like the war in Afghanistan or Iraq as everyone will mention that, but look at different and interesting aspects such as NATO's contribution (or not depending on your outlook) to Afghanistan. The internet and broadsheets are also good sources, - often worth reading those on both sides of the political divide to get a balanced perspective; from this you can form your own opinions on the issues, but be able to back them up with reasoned argument - there are no right and wrong answers, but rather fewer 'right' approaches to expressing your opinions and why you hold them and many 'wrong' ways of doing it. It is a measure of your ability to hold interesting conversations on various subjects, without rubbing people up the wrong way, while still presenting your own thought process without following the flock and repeating 'parrot-like' the fashionable bandwagon 'wisdoms'.