ITunes does not open when icon is clicked

Question

Ever since I downloaded the latest update for iTunes, it has refused to open. I went through the troubleshooting page, but they all related to installation issues, and this seems to have been installed, just not accessible for some reason. I have completely uninstalled and reinstalled iTunes and QuickTime three times (including all related temp files). QuickTime seems to be working fine, but iTunes still does not respond.
*The previous iTunes update I downloaded from Apple also caused problems (mainly a notice that there was an error every time I opened the program). Because the program still seemed to work fine, I would just progress through the notices every time.

Answer 1

I think from what you are saying that iTunes persits in the task manager.
This means that something is blocking it from completing its start up.
There are a couple of things to think about. Spyware can do this so run a full virus and spyware scan with upto date definitions.
Sometimes security software can do this, although I haven't seen that for a while. Try starting iTunes with your firewall off. If it starts it is a sign that you need to reconfigure your firewall.
Plugins for itunes can do this, do you have any, even if not the ones I mentioned.
Another possibility is that there is soemthing esle on your PC interfering with iTunes, you can use MSCOnfig to invesigate this. Here is an article telling you how.
http://docs.info.apple.com/article.html?artnum=302538
It is worth working through the original article I gave you. Starting iTunes in another account can be very helpful - even if you have to create one to do it, as some problems are account specific and others system wide.