I tried everything but nothing worked to make iTunes Store functioning on my computer. I even uninstalled and re-installed iTunes... three times! And still the iTunes Store wouldn't come up. When I ran the Diagnostics tool it gave me some crap about how iTunes Store couldn't make a secure connection.
Well, as of about an hour ago it's finally working again! It took me the better part of three days of actively addressing the issue and a whole wazooload of Google searches. Lo and behold the solution came from a YouTube user named audsmithl15, who posted it as a comment on a video demonstrating the exact same problem.
Here is what audsmithl15 came up with. I'm re-posting it here, for sake of anyone else who might be searching for the fix...
1. Go to C:\ProgramData\Apple\InstallerCache\AppleApplicationSupport 2.0.1Took less than 10 minutes to apply the fix and after that, iTunes Store comes up fine!
2. Right click
4. Go to C:\ProgramData\Apple\InstallerCache\AppleApplicationSupport 1.5.2
5. Right click
7. Restart PC
Bigtime props to audsmithl15 on YouTube for hitting on the solution :-)