Firewall issues

I've set up a iptables firewall on my RH7.2 box, but I'm running into an 
odd problem.  After I set up the firewall, everything works fine for a 
few hours.  But after a while (not sure the exact amount of time), the 
computer stops responding to requests on the open ports.  Looking at the 
output from iptables -vL, I can see the requests coming in and passing 
the appropriate rule, but then nothing happens (almost as if the packet 
is dropped).  Here is the firewall as I have it set up:

iptables -P INPUT DROP

# create our own chains
iptables -N allow
iptables -N block
iptables -N logdrop

# what to allow
iptables -A allow -m state --state ESTABLISHED,RELATED -j ACCEPT
iptables -A allow -m state --state NEW -i ! eth0 -j ACCEPT  # allow lan
iptables -A allow -p icmp -j ACCEPT                     # pings, 
traceroute, etc
iptables -A allow -p tcp --dport ssh -j ACCEPT          # ssh
iptables -A allow -p tcp --dport ftp -j ACCEPT          # ftp
iptables -A allow -p tcp --dport 62000:64000 -j ACCEPT  # passive ftp

# explicit blocks
# netbios broadcasts..  no point in filling the logs with them
iptables -A block -p tcp -i eth0 --dport 137:139 -j DROP
iptables -A block -p udp -i eth0 --dport 137:139 -j DROP

# log and drop
iptables -A logdrop -p tcp -m limit --limit 3/s -j LOG --log-level 6 
--log-prefix "TCP Dropped: "
iptables -A logdrop -p udp -m limit --limit 3/s -j LOG --log-level 6 
--log-prefix "UDP Dropped: "
iptables -A logdrop -p icmp -m limit --limit 3/s -j LOG --log-level 6 
--log-prefix "ICMP Dropped: "
iptables -A logdrop -f -m limit --limit 3/s -j LOG --log-level 6 
--log-prefix "FRAGMENT Dropped: "
iptables -A logdrop -j DROP

# set the user defined in INPUT
iptables -A INPUT -j allow
iptables -A INPUT -j block
iptables -A INPUT -j logdrop

The machine has 3 ethernet cards (one not being used).  eth0 is the 
connection to the outside world and eth1 is on the local lan.  I set up 
the block chain because I was getting so many NETBIOS hits it was 
rediculous.  I have tried changing the INPUT tables policy to ACCEPT, 
but it still doesn't work..

Any help would be greatly appreciated.

-- 
Trey Gruel
[email protected]