I'm having the same problem, but in addition all the tree sprites are "flashing". They don't go in and out of existence, they flash from all white to normal. It's very festive. Processor 2.9 GHz Intel Core i5 Memory 8 GB 1600 MHz DDR3 Graphics NVIDIA GeForce GTX 660M 512 MB Software OS X 10.9.1 (13B42)