FreeBSD 5.4-p8 PPPoE Link Problems...?

[perikillo]

   Hi people.

     I have one ISP that give 512Kbps service, they give to me one
modem SpeedStream, i setup everything, before this service was running
on freebsd 4.11-p16(i think ...?), them change all to freebsd 5.4-p8.

    The problem here is that sometimes appear the link up:

tun0: flags=8051<UP,POINTOPOINT,RUNNING,MULTICAST> mtu 1492
        inet 201.143.64.40 --> 201.130.144.1 netmask 0xffffffff
        Opened by PID 236

    But if i try to access the Internet, the browser say that i dont
have connection, them i go to my freebsd box, test the connection with
Ping and is correct i lost my connection, i need to manually force the
link to close and again connect.

     I dont know if this problem is from my ISP or is Freebsd, i dont
have a clue where to find the problem to fix this, with freebsd 4.11 i
have this problems to. This is my /etc/rc.conf for ppp

# User ppp configuration.
ppp_enable="YES"                # Start user-ppp (or NO).
ppp_mode="ddial"                # Choice of "auto", "ddial", "direct" or "dedica
ppp_nat="NO"            # Use PPP's internal network address translation or NO.
ppp_profile="prodigy"   # Which profile to use from /etc/ppp/ppp.conf.
ppp_user="root"         # Which user to run ppp as

    I was thinking to create a script that check every 5 minutes the
link and do something to re-connect, but i dont think is the right
solution.

    Does someone have any idea what can i do  to find the problem and
fix this...?

    FreeBSD 5.4-p8
    Firewall IPFILTER

    I have everything enable on the kernel not from modules.

     Thanks all for your time.