WinTame2012: Interesting idea about the wifi power draw being affected by the antenna. I had installed 9dB antenna's on mine, which have now been decommissioned, of course. Above, senseless says that he was not using wifi when the chip was burned, but it was still enabled. No doubt he wasn't using an antenna, if he wasn't using wifi. And that is the scenario during which his chip was burned.
Yes, I think the Wi-Fi interface is working in the bridge mode in Avalon so it can still be powered while is 'not used'. And without antenna attached PHY layer have to ramp up its power to have more/less stable signal while just listening around. Xiangfu said that this happens not on all TP-LINK units so probably there is HW bug in some SoC revisions which is related to power management as well.
If anybody with fried USB hub chip care to share his antenna condition (attached or not) this would clear this guess up a lot.