ttyUSB0 console deosn't work on 2.6.31-5

Using a USB serial cable (with the pl2303 chip)works great as a serial terminal when the system is up via /dev/ttyUSB0. When I add “console=/dev/ttyUSB0” to the kernel parms in GRUB it causes the system to panic in tty_open after a few lines of the boot output do come out on the USB serial terminal. I also notice that kdb complains that it cannot find a console (looking at code that console_drivers is NULL). Is there something I’m missing in my initrd, or in the .config for the kernel build to have all the needed pieces to make this work?? Thanks!