Did you adapt for stratum protocol when the change was made? Cube supports getwork protocol and Slush changed to stratum. I have to run my Cube's through a Raspberry Pi to proxy.
If I understand your question correctly, I am running slush's stratum protocol proxy, as seen the the last two screenshots. I am using slush's miner proxy version 1.5.5 on two different Win 7 64bit machines. Whole setup is hardwired to a Netgear Gigabit Router (WNR3500) then to cable router. No wifi on the whole network. Nothing on the firewall logs. No additional firewalls on Win 7 machines beyond default firewall. I've tried swapping out the lan cables.
****************Forgot to mention: Corsair CS650M w/ 51 Amp 12v rail.