Airport Express 802.11g disappears
I have an Airport Express 802.11g that's not happy. It's set up to run in client mode on my existing WiFi network, and I'm only using it to stream audio to. It's running firmware 6.3, which I think is the most recent for this old model. When I power it up, it joins my network successfully, is visible in Airport Utility, and is selectable as a target for AirPlay in iTunes from both my Mac Pro and iPhone running Apple Remote. After about 1 minute, it simply vanishes from the network, and Airport Utility and iTunes can no longer see it. The unit still displays a steady green light. If I power cycle it, the same sequence repeats. If I factory reset it, set it up from scratch, the same thing happens again.
My base station is a 'Neufbox', standard issue by my ISP (SFR, in France), and I don't have any difficulty with other wifi devices on the network.
Any ideas?
Airport Express-OTHER