This issue has been complained about in:
http://forum.mikrotik.com/t/rb750-cpu-usage-problems/58008/1
http://forum.mikrotik.com/t/flash-on-profile/59461/1
http://forum.mikrotik.com/t/rb751u-2hn-frequent-daily-reboots/53849/1
and exists on at least RB750GL, RB750UP, RB751 and RB2011 from our experiences.
I am working with Mikrotik support on this, please log a ticket with them by emailing support@mikrotik.com and attach a supout.rif created around the time the problem is occurring.
The more people that provide them with supout.rif’s the faster they should be able to find the problem.