what hardware config are you using? e.g. mini running osx, bootcamp, etc
I have managed to properly configure my Belkin MIMO G wireless adapter to setup an ad hoc network. It will work fine, but when I reboot, the SSID disappears and I can't reconnect without unplugging and plugging in the adapter first.
Usually, the belkin driver starts a program when it detects the adapter being plugged in. I added that program to my setup items, and it starts at boot, but the wireless network still doesn't appear until I unplug and replug the adapter. Any ideas?
And how is it attached to the Mini? Is it attached to Mini directly? A hub that is attached to the Mini? A hub powered by you power supply?
If it is not powered from the Mini's bus, it could be that the Mini is not seeing it when it wakes up/boots when you start the car. I saw this with my external sound card when it was off my P5V powered hub. Once I plugged it directly into the Mini, all was well.