Thanks for the tip - I hadn't been using a USB power supply to the HDMI-to-VGA adapter, but if I find that the new adapter won't work without a 5v supply, then I'll use the Netgear 5v USB power supply which I've been using with a (now redundant) Ethernet bridge. It's tried and tested, so should be fine. But as I say, I hope that I won't need to use it.