Hey, I had a similar experience that I reported in the v7.2-topic: http://forum.mikrotik.com/t/v7-2-is-released/157082/1
Update from 7.1.5 to 7.2. results in massive packet drop, unresponsive router. The box is a CCR1009, I had dude on it previously, but migrated it to another box before update to v7. Switching to a second partition with 7.1.5 brought the previous running state back. I know that this is not very detailed, but as this is a production router I don’t have the time now to debug the problem. Maybe next week I will be able again to play a bit with 7.2 but it is interesting to see a similar/same problem on a CCR1009.
UPDATE: The problem was solved once I configured my CAKE queue types correctly. As long as I had CAKE in simple queue with bandwidth parameter set, I could trigger the packet drop/latency by enabling and disabling the simple queues.