Steam Error: The specified subscription is not available for credit card purchase

This error is caused by outdated copies of the Steam purchase pages residing in your Internet Explorer browser cache.

Please observe the following process to resolve the error:

1. Close the Steam application
2. Open Internet Explorer and go to "Tools" > "Internet Options..."
3. Click the "Delete Files" button and then click the "OK" button in the dialog box which opens (this process may take some time to complete - you may wish to adjust the Temporary Files cache in Internet Explorer to ensure excess information is not cached in the future)
4. Close Internet Explorer and restart your computer
5. Load the Steam application and locate the subscription you wish to purchase