Former N-Dubz singer Tulisa stands accused of attacking writer Savvas Morgan at the festival in Essex last August. She denies the charges, adding that she had her hands behind her back at the time of the alleged altercation.
Judge Angus Hamilton added that he was keen 'this does not go on any longer than necessary,' but that they needed the adjournment to call extra witnesses.
Tulisa's assistant, Gareth Varey, is also on trial for threatening behaviour. He too denies the charge.
The alleged victim claims that Tulisa swung her arms and fists in the backstage area at the festival, and that he was left with swelling to his eye after the attack.
However a photograph showing Mr Morgan's injuries has now been lost.
Tulisa meanwhile has claimed the blogger has a personal vendetta against her, after she asked for him to be removed from a VIP area at a nightclub. She also voiced suspicions that he was involved with leaking her sex tape online.
The trial resumes in July.