I have the same problem on 10.6.3.25 on an x64 Windows 7 box.
I have created a command file which kills all the iTunes processes, and then restarts a couple of them. This allows iTunes to be "closed", and then restarted without a complete reboot.
You have to run this as Administrator (elevated command prompt). It kills the iTunes process, and the other processes that iTunes spawns. It also stops the Services that iTunes depends on, and restarts the ones that are automatic.
taskkill /im itunes.exe /F
taskkill /im APSDaemon.exe /F
taskkill /im distnote.exe /F
taskkill /im syncserver.exe /F
net stop "Apple Mobile Device"
net stop "Bonjour Service"
net stop "iPod Service"
net start "Apple Mobile Device"
net start "Bonjour Service"