With every new jailbreak, there are a few problems here and there. One of the major problems with the iOS 5 jailbreak was iBooks. Today, iH8sn0w managed to get iBooks working on a jailbroken iOS 5 device.
The issue was dealing with how redsn0w/sn0wbreeze did sandbox patches in the kernel. For those that don’t know, sandbox is a security measure that is used to ensure applications such as Safari don’t have access to personal information or system files. - iH8sn0w