I think a good CIO should be:
– a leader
– He/she should have some level of knowledge in many IT fields, and should have the ability to build a team of people who have the technical skills needed to the day to day tasks, while he/she focuses on the strategical goals.
– a good comunicator
And answering your question, I think he/she needs to have some technical skills (not necessarily <i>too</i> strong), and he/she <i>must</i> have great people skills.