traffic load on the network loses it falls and must rebooted Etherne

hi

I have a os mikrotik on a server ESXi 5.5
i work with mirkotik 2 years without any problem
now we have problem
When the traffic load on the network loses it falls and must rebooted Ethernet for back to internet
i have only ipip service for the movement of traffic on the router

i remove and reinstall mikrotik os and reconfigure but not solved

can any one help me ?