Apple has released iTunes 9.2.1 for both Windows and Mac OS X,which according to the release notes includes a number of bug fixes such as issue upgrading to iOS 4 on an iPhone or iPod Touch with encrypted back-ups.
It is available via Apple Software update and is around 65MB in size.If you have jailbroken your iPhone, iPod Touch using Spirit Tool then stay away else you will loose your Jailbreak. We recommend you to wait to see if Apple has included some new way to fix the exploit. iTunes 9.2.1 provides several important bug fixes.Full change log is as follows.
*Disables older versions of some incompatible third-party plug-ins
*Addresses minor issues with dragging and dropping items
*Addresses a performance issue when first syncing to some devices with iTunes 9.2
*Addresses an issue upgrading to iOS 4 on an iPhone or iPod touch with encrypted back-ups
*Addresses other issues that improve stability and performance
Download iTunes 9.2.1
Download iTunes 9.2.1 for Windows and Mac
Musclenerd has confirmed that iTunes 9.2.1 is safe for all jailbreakers and unlockers.