mpd4 cann't work after upgrade freebsd os

[Pei Pjf]

Dear list
 when I upgraded freebsd os from 5.1-->5.5-->6.0-->6.2, all works
 fine but mpd can not work well.

mail# mpd4 -k
Multi-link PPP daemon for FreeBSD
process 4120 started, version 4.1 (root at mail.topcomtech.com.cn 00:52 25-May-2007)

CONSOLE: listening on 0.0.0.0 5005
[myisp] can't create socket node: No such file or directory
[myisp] using interface
[usr] can't open /dev/cuaa1: No such file or directory
[myisp] IFACE: Open event
[myisp] IFACE: Up event
[myisp] can't set bpf node program: Bad file descriptor
fatal error, exiting
[myisp] IPCP: Close event
[myisp] IFACE: Close event
[myisp] can't shutdown ":": Bad file descriptor
[myisp] can't shutdown "bypass.inet": Bad file descriptor
[myisp] can't shutdown "bypass": Bad file descriptor
process 4120 terminated

mail# uname -a
FreeBSD mail.topcomtech.com.cn 6.2-RELEASE-p4 FreeBSD 6.2-RELEASE-p4 #1: Wed May  2
+23:01:31 CST 2007     pjf at mail.topcomtech.com.cn:/usr/obj/usr/src/sys/MYKNL  i386

mail# kldstat
Id Refs Address    Size     Name
 1    1 0xc0400000 3d7d60   kernel

Though I googled Internet, read mpd douments, I don't how to deal with this case.

Thanks in advance.

peter