The long trusted jailbreak tool redsn0w has been updated again to fix iBooks issues. The iPhone Dev-Team, and particularly planetbeing this time, have issued the update which addresses an issue some have been having with DRM and iBooks.
redsn0w version b5 incorporates yet another fix for iBooks, this time involving DRM. @planetbeing wrote a utility called "crazeles" that overcomes jailbreak detection by iBooks that would cause about 10% of images to show incorrectly. This fix is similar to the "hunnypot" fix that @comex wrote for the 4.x jailbreak. As usual, you can choose to install the fix either by re-running redsn0w over your existing jailbreak (de-select Cydia if you do that), or by installing the corona package from Cydia (it's the same set of files no matter which way you choose).
In related news Corona, the Cydia tweak that allows your tethered jailbreak to be untethered, has also been updated to fix this issue. If you have installed the Cydia tweak you will see an update in Cydia for the tweak (if you haven't already).
Click here if you want some tutorials on how to use redsn0w to jailbreak your device.
Hi, I heard some great news from IRC @planetbeing has fixed Corona issues with iBooks DRMd books. Corona 1.0.6 to be released soon.