Some more debugging tried: See this thread for details, but basically I reflashed to the older firmware, got kismet up and running, set up boot from MMC, then flashed the new image onto the device, then booted from MMC, so I was running the old image. However, due to the way dual-boot works, this means I have the old image running on the new kernel. Kismet behaved the same way as with the new image, it started up, and quit scanning in 3 seconds. I guess this means it's some sort of kernel issue?

I tried both the original and Scegliau's cx3110 drivers, with no difference.