Oddball IPTables problem

[paleck]

I have a couple of Centos4 boxes set-up as routers currently and have run into an odd problem. There are some devices that have public IPs behind a these linux routers. If I unload all the rules I can access those devices, if I enable only the most basic iptables (with default allows for all public routable IPs) then I cannot access those devices. Anyone seen this or have any ideas?

I should note that it doesn't stop all traffic, but what it appears to do is allow me to download approximately 60-64k and then stop the connection before it is finished downloading.