HTRegz: nebulus is right, it could be from an overly large ethernet segment.

There are switches available these days which are capable of doing their own ARP caching and sending fake ARP responses to hosts, thus vastly reducing ARP traffic (ARPs are no longer broadcast unless the switch doesn't have it in its cache).

On a heavily populated network (Say >100 hosts), it would be advisable to use such a switch.

However there are other types of broadcast which are sent by default on many OSs which will also flood a LAN with messages if it gets big enough - the primary candidate will be Windows name resolution (NMB) broadcasts - assuming most of the machines are Windows (although obviously Samba will send them too on Linux for example)

Try counting the number of distinct IP addresses from the logs (you might have to make a script to do this) to see how many hosts there are

Slarty