Hello,
Please check my other posts regarding this issue,
http://forum.mikrotik.com/t/rb493ah-ethernet-ports-stop-routing-then-restarts/26396/1
and
http://forum.mikrotik.com/t/rb411-ethernet-freezes-no-receive/22193/1
Hopefully Mikrotik will resolve this serious issue. Please add your experience with this problem with as many details and tests as you can in order to help MT re-produce the problem and workaround a solution.
Many thanks