iTunes 9.0.3 and 9.1 may crash on launch after the Mac OS X 10.6.3 update is applied. It appears that this problem is caused by the absence of files removed from Flip4Mac by Monolingual, a tool for deleting extraneous languages from Mac OS X. As such, if you’ve run Monolingual on your Mac and have Flip4Mac installed, you may encounter the crashing issue after updating to Mac OS X 10.6.3.
In most cases, the solution for this problem is to reinstall Flip4Mac, which will replace the missing files. Simply download the installer and re-run it.
If this does not solve the problem, try first uninstalling the FLip4Mac WMV components using the file Flip4Mac WMV Uninstaller.pkg, which should be in the Flip4Mac folder in your Applications folder but can also be accessed by downloading Flip4Mac again.