It's working for me in Windows 7 Ultimate 64 bit. Here is what I did. Some of it might be overkill but after reading the problems you guys had, I didn't want to take any chances.
- Logged into the Administrator account
- Uninstalled iTunes and Quicktime from the Control Panel
- Right clicked the iTunes exe file and "Run as Administrator"
- After the install, I right clicked the desktop icon and "Run as Administrator"
- After iTunes opened, I closed it.
- Logged off the Admin account
- Logged into my regular profile
- Right clicked the iTunes desktop icon and "Run as Administrator"
- Library updated and it's working fine
Hope this helps. Good luck.