Finally got an email from the itunes store support people with a solution that actually worked. It's included on this new page specifically for the 11333 error:
http://docs.info.apple.com/article.html?artnum=306628. Before this I had tried everything suggested and nothing helped.
These are the instructions - if you are using Firefox you should
right-click on the links and choose 'save link as' then follow the instructions for installing the certificates:
"It is possible that iTunes is unable to verify the validity of your security certificate due to an issue with your Certificate Revocation Lists. To resolve this, first download and install the server1.crl file from Entrust:
Download this file:
http://crl.entrust.net/server1.crl
In the resulting dialog box, click Save and save the file to your desktop.
Click Close when the file has finished downloading.
Right-click the server1.crl file on your desktop and choose Install CRL from the shortcut menu.
Click Next.
Ensure that "Automatically select the certificate store based on the type of certificate" is selected.
Click Next.
Click Finish.
Click OK.
Next, download and install the net1.crl file from Entrust:
Download this file:
http://crl.entrust.net/net1.crl
In the resulting dialog box, click Save and save the file to your desktop.
Click Close when the file has finished downloading.
Right-click the net1.crl file on your desktop and choose Install CRL from the shortcut menu.
Click Next.
Ensure that "Automatically select the certificate store based on the type of certificate" is selected.
Click Next.
Click Finish.
Click OK.
Once these Certificate Revocation Lists have been imported, quit iTunes if it is running and then open iTunes again. You should now be able to access the iTunes Store."
And now I can connect to the store again with 7.4.3.1. 😝