It seems that Android needs almost two resets to be recognised(it needs to arrange internally its drivers or the hardware). Every time I've changed the ROM, immediately it isn't seen by the PC host. And then I always fall into the mistake of installing "new" drivers. Suddenly, I don't know why, all starts to work fine, usually after resetting the kindle several times....
Oh pardon, I've not read it correctly. In CM 10, if you are already inside "Storage Device" you can see the simulated sdcard as a "0" directory.