GreenPois0n tool have been updated by the Dev Team to give support for the iPod Touch 2G ( MC and Non MC models) on iOS 4.1. You could now use GreenPois0n on Windows, Mac OS X or Linux to jailbreak iOS 4.1 on iPod Touch 2G. You could get the updated GreenPois0n tool from the official website.
Follow the guide posted here to jailbreak iPod Touch 2G Â (MC Model also) on iOS 4.1 using GreenPois0n.
Download GreenPois0n from here.