Starting from the 1.0.beta3, serial console redirection had been disabled during the boot in the standard compactflash image. Maybe this is a problem for net4801. Could you try with the WRAP compactflash version? In that version I have not disabled the redirection. In any case you should configure (from the BIOS) the RS232 of the Soekris to work at 38400 instead 19200.