Why can't you declare war?

You have to speak to your victim and choose 'Declare War' from the options on the left.

That option isn't there, only other races pop up. I guess I should mention that I had good relations with this race, maybe that's why? A lot of races kept appealing to me for help against them (they were too influential), but all I said was "Blah blah, but they're our friend, etc."...

To declare war in Dread Lords, you need to either attack the civ in question with a ship or tell ANOTHER race that you'll declare war on them.

In the expansion, there is a declare war diplomatic option.

I have Gold Edition, which has the expansion, and that option isn't there, I say.

Are you playing DL or DA, though? As noted by others, the Declare War option is only in DA.

It is also on your side of the panels, with the treaties that you can propose to them.

I just double click the Galactic Civilizations II - Gold Edition icon on my desktop to play, but the Dark Avatar movie plays and the bottom left screen shows "Dark Avatar v1.50x3" (or whatever version it is, my memory stinks).

Still not there. Maybe if you have good relations with the person you can't declare war... I'll try a new game and see if it comes up.

Have you concluded any contracts with the referring race? In that case, you have to break all contracts first. Then the "declare war"-button will appear...

If the contract is concluded, wouldn't the contract end?