I used Alice 3.0 as a 10 day unit in my Technology Topics class. Much better characters and animation than 2.2. However, about half (class of 24) of the students in each class saw their worlds freeze each day. Could not manipulate objects in their world. Only fix was to quit and reload Alice and their file. OK for a short unit, but I would like to use it in the fall for my programming class. Not usable after this experience. We run in a lab environment with Mac OS 10.5.8. If anyone has had this experience and solved it, I would appreciate any suggestions. Thanks!