Yep. Another limitation of the physics movement. The physics engine updates before your event sheet runs, so all physics collisions occur before you're even able to test for a sprite collision. So for all intents and purposes, your sprites will never collide. It's a problem that's been brought up before by a few people.
To get around it, you could make your bricks non-physics objects and code your own collision routine that manually sets your ball's bounce angle and speed. It would take some work, but it could be done. Or you could wait until there's a fix for the physics collision problem. Sucks, I know, but hey... Construct is still just in beta right now so there are limitations.