if you are a getting an error when u download ur package from installer 4.0b6-5 after u download leys say chopper, u try and open it and it says the application chopper could not be opened, then try this, through your ipod on the ground... No im kidding, i almost did. This only works for 2.0 jailbroken ipods or iphones, it worked for me and like 6 others so far.

1. Reboot ur device
2. Go to appstore
3. Download a random free app
4. Reboot
5. Open it and wait for it to boot
6. Then close the app.
7. See if ur installer app works
8. If so DO NOT delete the appstore app, th installer app wont work again.
9. If the installer app still wont work reboot again

This may or may not work for you
Comment me on info plz