Did you try using another kernel, like for instance the latest hacked kernel for the C3000 on Tetsu's site? I'm using v18a, and the serial stuff is built-in (i.e. not in a module), and it handles my GSM/GPRS CF card gracefully. When looking a the dmesg output, I see a lot of stuff related to adjusting the voltage when I insert/remove the card in the Zaurus...