Compiled new kernel, now dial-up serila modem won't connect

I just compiled a new 2.6.14-rc4 kernel using makeconfig, into the Ubuntu 5.10 distro.

Everything boots fine, but the modem, which dials out, then quits as soon as the "handshake" is over. Booting back into the old kernel that came with Ubuntu, it still works fine.

Here is the text of that section of my config file:

# Wan interfaces
#
# CONFIG_WAN is not set
# CONFIG_FDDI is not set
# CONFIG_HIPPI is not set
CONFIG_PPP=y
# CONFIG_PPP_MULTILINK is not set
# CONFIG_PPP_FILTER is not set
# CONFIG_PPP_ASYNC is not set
# CONFIG_PPP_SYNC_TTY is not set
# CONFIG_PPP_DEFLATE is not set
# CONFIG_PPP_BSDCOMP is not set
# CONFIG_PPPOE is not set
CONFIG_SLIP=y
# CONFIG_SLIP_COMPRESSED is not set
# CONFIG_SLIP_SMART is not set
# CONFIG_SLIP_MODE_SLIP6 is not set
# CONFIG_NET_FC is not set
# CONFIG_SHAPER is not set
# CONFIG_NETCONSOLE is not set
# CONFIG_NETPOLL is not set
# CONFIG_NET_POLL_CONTROLLER is not set

Where have I gone wrong?

Figured it out for myself, I did not realize I had to say "Y" to:

# CONFIG_PPP_ASYNC is not set

Hint to all using menuconfig: the "Help" feature is impressive, I recommend using it extensively.