Aggression at dog park

I have a 2 year old Husky mix who up until just recently, has been the perfect dog. I've been taking her to the dog park since it opened (about 3 months now), on a very regular basis (about 3 times a week). The last time she was there, she had a problem with aggression towards one dog when toys were involved. We have never seen this with humans. And she's always great with other dogs when toys aren't involved. But as soon as another dog has a toy, she doesn't want them to have it, and she'll fight over it.
It's happened about 2 times now (twice in one night), and I've always broken up the fight. I just don't know what to do with her now. It's just very strange that she started showing aggression out of the blue like this. Is there anything I can do to get her to stop this toy aggression, or do we have to give up the dog park?