Found the relevant adjudication on the ASA website.
In summary, The ASA banned the advert on the grounds it was "offensive and irresponsible", and "unsuitable to be seen by chilrden". Pointedly, they DISMISSED the complaints on the grounds of racism.
I don't personally think the ad was "offensive or irresponsible". Nevertheless the code is there, ad agencies are aware of it (or should be), and the adjudication process is transparent (unlike the MPAA, for example). The decision is fair enough.
Link:
http://www.asa.org.uk/ASA-action/Adjudications/2010/12/Sony-Computer-Entertainment-UK-Ltd/TF_ADJ_49542.aspx