Had you emptied the Save folder, which defaults to C:\Users \UserName \Documents \SH4 after you activated FotRSU v1.8? It uses quite a few "assets" differently than the Stock or any other modded game, and if you do not empty the Save folder, the game does not run correctly. That also applies to most major mod configuration changes with JSGME, but is dependent upon what is changed when doing so. If you still have FotRSU activated, run its JSGME and choose "Tasks..." in the middle, then "Export activated mods list to --->" and choose either "Clipboard" or "Text file", and paste the info into your next post. As an aside, there is a partial English translation in the SubSim downloads somewhere for v2.x of FOTRS. It is a beautiful looking mod, and is what FotRSU was built on, along with combining v1.2 and v1.3 of the SH4v1.5 mods. You will most likely find that the AI is quite persistent in FOTRS v2.x
