Carputer - UPnP fails when eth0 is disconnected

[blk_addr]

Hi all,

I got into XBMC a few months ago and love it - just got a Pi a week and a half ago and have been fighting one last problem trying to get my carputer media server up. I'm hoping someone here knows Linux network configs a lot better than I do!

Here's where I am:
- Netis WF-2116 wifi adapter (RTL8192CU chipset) up as standalone access point, dnsmasq serving IPs fine on wlan0; IP 192.168.2.1

- eth0 set up for home network, static IP served by router 192.168.1.132

- Pi and all peripherals powered via powered USB hub

What I plan to do:
- run the Pi headless in the car for a cross-country drive in June, serving media via UPnP to an HP Touchpad (CM9 Nightlies Android) via Android XBMC and multiple IOS devices via Airplayer and Goodplayer apps

With the eth0 cable plugged into the Pi, everything works dandy with all devices. I can disconnect the cable and all is still well.

If I boot with the cable disconnected, I can stream fine to XBMC on the Android tablet. I can browse movies fine in Airplayer but the movie never loads - eventually it will load 60-90+% but spins forever at that point. Goodplayer also allows me to browse content but crashes immediately when I try to play the movie.

With a movie hung loading (in Airplayer) I can connect the Ethernet cable and BOOM the movie immediately plays. I can then disconnect the cable and all devices continue to work flawlessly. I can drop off my xbian AP, re-join, and it still works. I can introduce a new device and it works fine too. But if I reboot, I'm back to square one.

When I connect the Ethernet cable and run dmesg, I get the following line:
"smc95xx 1-1.1:1.0 eth0: link up, 100Mbps, full-duplex, lpa 0xCDE1"

After fiddling with eth0 as manual/manual bridged/static/dhcp I finally got it to work with some combo of Manual and allow-hotplug eth0, but I had no more Internet access over that interface - so I fixed that and broke my carputer streaming! Now I can't go back (because at 4am I crazily decided to mod interfaces without backing it up) but at least I know I can get it to work.

I just finished starting completely from scratch on a new SD card and am stuck with the exact same symptom. Does anyone have any ideas?