Rejechted

I am running Tekkit server 1.2.9e which uses version 1.6.8f of Extra Cells. I want to update Extra Cells to 1.6.9e without touching the rest of my server. When I replace the JAR with the newer version of Extra Cells, forge mod loader fails to load with: [sEVERE] [ForgeModLoader] There was an ID conflict in extracells! Shutting down now! This seems like it should be something fairly trivial to do, but I'm stuck.