As propbeanie said, computer specs would be nice to have in order to error-check. However, I used to run SH4 on an old Dell with 500mb RAM, so I doubt that's an issue.
My first step would be to disable the mod and see if your problem is still there. Next step would be lowering graphics settings (if that makes a difference) and, finally, uninstalling and reinstalling SH4 vanilla. Make sure to back up your files first before you do that, though.
