I'm experiencing the same problem described in this post: http://forum.mikrotik.com/viewtopic.php ... it=rb750up , but with the latest RouterOS version 6.10. I guess it was supposed to be fixed by previous versions.
My setup is very simple:
power via DC jack
eth1 not used (no nat, dchp, etc...)
eth3 poe-auto, master port eth2
eth4 poe-off, master port eth2
eth5 poe-off, master port eth2
Ports 2,3 powers up two devices (metal 2Hn) and I access the RB750UP using winbox via eth4 that's in the same switch with ports 2,3,5.
Even opening the device window or entering the poe panel to just see power consumption, PoE starts going up and down randomly. Closing winbox everything is working well and stable.
I accessed the RB750UP via mac address, since eth2 has an IP assigned on a different subnet from my PC (I'm testing a setup for a remote site), if this can be of any interest.
Is anyone having the same problem with the latest version? Any idea?