I had a similar situation. Torian declared war on me. So I started attacking them, conquering a few planets. They have not come close to any of my planets, so the war is going very well for me. At first they offer to "pay" for a ceasefire, but I turned them down because I didn't think I was done with the war yet. Now, suddenly, I'm forced into a ceasefire with them and have to pay them resources! That is not going to happen, so I guess I'm done with GalCiv IV
I'm not spending another 18 hours to have this happen again. If I ever feel like playing GalCiv again, it is back to GalCiv III for me...