have you guys tried a complete reinstallation of itunes?
From the control panel, is you're using windows, get rid off itunes and quicktime. get into the program files folder and delete quicktime folder, then in C:\windows\system32\ search for quicktime file and delete it.
Make sure the option "show all hidden files and folders" is enabled, under Tools-Folder Options-View tab. Visit Documents and Settings in Local Disk C, under your username or owner, sometime administrator, locate the application data folder and delete "apple computer folder". Do the same under Local Settings. Empty the TEMP folder and the Internet Temporary Folder. Remember to empty the Recycle bin.
Restart you computer (can use MSCONFIG if you're comfortable with that see
http://docs.info.apple.com/article.html?artnum=302538).
Lastly, from the apple website get a fresh and clean download. Agree with all the default settings.
Hope this may help.