As soon as there is ddos attack or high packet rate on simple queue CCR cpu usage goes to 100%. My other post testing ccr have details
ccr 1016 screwed up @ 300k pps udp 64b packet by a simple queue of 900Mbps. Support asked me to upgrade to 6.24. Even after upgrading problem still is same
Did you find the solution ? i have same problem http://forum.mikrotik.com/t/queuing-100-cpu-usage-on-ccr-sometimes/89975/1