Are you running any of Symantec's (Norton) or McAfee's Internet security products or anything similar, or an antivirus/antispyware application? Some such utilities treat an upgrade to iTunes as a new application and can block the application from connecting. So you have to go in and reset the utility to allow iTunes. The same thing can happen if you upgrade the security product (this has particularly been a problem with recent McAfee upgrades).
Check the settings for your utility. If iTunes is still listed, remove and re-enable the exception for iTunes. Consult your utility's documentation for the appropriate procedure. If you have Norton, you can find instructions for that utility on Symantec's web page for iTunes. You may also need to check the built-in Windows firewall as well.
Hope this helps.
Close your iTunes,
Go to command Prompt -
(Win 7/Vista) - START/ALL PROGRAMS/ACCESSORIES, right mouse click "Command Prompt", choose "Run as Administrator".
(Win XP SP2 & above) - START/ALL PROGRAMS/ACCESSORIES/Command Prompt
In the "Command Prompt" screen, type in
netsh winsock reset
Hit "ENTER" key
Restart your computer.
If you do get a prompt after restart windows to remap LSP, just click NO.
Now launch your iTunes and see if it is working now.
If you are still having these type of problems after trying the winsock reset, refer to this article to identify which software in your system is inserting LSP:
iTunes 10.5 for Windows: May see performance issues and blank iTunes Store
The latest windows version of itunes had been unable to access the internet (while all other applications, including Firefox, could access it just fine) for going on a week.
netsh winsock reset - and a reboot
fixed it for me. Thanks.
For the future reference of others - how to use autoruns is in a link posted above which I'll repeat:
I have bsecure cloudcare for my family- its excellent for anyone who has kids. But checked the log and never said it was "blocking" itunes and even added it as "OK" program just in case. I have been pulling my hair out for weeks as not able to connect to itunes store. I did all the other suggestion (reinstall, shut off all firewalls, popups). I did the autoruns thing the only thing I had on Bsecure, went to their FAQ and #1 was a patch to fix "unable to connect to itunes after 10.5" ran that program took 10 seconds, rebooted, and now I can connect!!! YEAH!