The payload fixes the "Main script execution failed" error and "Package download failed" error that some experience with Installer 3.x. Both these errors are related to a permissions issue.
If you have not used iLiberty+ for your iPhone, iPod touch it will rejailbreak it while installing this payload. To prevent losing your sources and installed apps you can backup the /var/mobile/Library/Installer folder using SSH, Term-VT100, or MobileFinder prior to using the payload.
If you have used iLiberty+ to jailbreak then only the fix will be applied.
Once the payload has been installed you can then upgrade to Installer 3.11 and overwrite the /var/mobile/Library/Installer folder with your backup.
The payload will also fix broken BSD. It works for 1.1.3 and 1.1.4.
You can download the Payload here. Also more information can be obtained at hackint0sh.