The New York Times (via Daring Fireball) provided some additional information on Steve Jobs' health, and the possible reason behind the announcement today that he was taking a leave of absence from Apple:

Two people who are familiar with Mr. Jobs’s current medical treatment said he was not suffering from a recurrence of cancer, but a condition that was preventing his body from absorbing food. Doctors have also advised him to cut down on stress, which may be making the problem worse, these people said.

Again, we here at TiPb wish Steve Jobs and his family the very best. Get well soon.