This might help, just as some troubleshooting...
- Make sure you've cleared your cache before you start a modded disk
- It could just be that the mod is outdated. (If you want one that is pretty easy and up to date then I would recommend DeadlyFishesMods)
- If you're hotswapping try to do it again
- You must be using verbatims for it to work as far as i know
Hope this helps its just some one of the problems i too have faced when trying to mod that game so these are most likely one of the things that is causing it.
Thanks Bengal for deleting my double post...