My configuration is really not complicate:

mining_proxy.exe --host stratum.bitcoin.cz --port 3333 --getwork-port 8332 --stratum-port 3333

Also tried 50btc and btcguild no real difference.

tried also different but I really don't think it is the proxy.

Concerning the Long Polling. It starts with long polling then disables it then a little bit later it makes restart.

Can you tell me what is normal state of the Miner? LED OFF or LED RED ??

I wait for the 750 corsair PSU hope this can help or I have an expensive brick.

The real problem is the restart. Is there possibility to login to the device and see more info with USB or this other service port?