Ok, this means that the issue is system wide. Let's try these steps:
1) Are you using any anti-virus software? If so, make sure it is up-to-date. If possible, I would recommend disabling it, better yet would be to remove it off the computer completely. Is the issue still happening?
2) If it is, the issue may lie with the iTunes Configuration file. Follow this article:
http://support.apple.com/kb/TS1776.
3) If it is still happening after that, put your computer into a selective startup which is shown in this article
http://support.apple.com/kb/HT1275. Try opening iTunes. If it still happens when under MSCONFIG then you may have an issue with the installation of iTunes. Go through this article
http://support.apple.com/kb/ht1925.
If after all that the issue is still happening let me know.