First try and delete the "downloads" folder that is currently located in your C:\Program Files (x86)\iRacing folder.
Then log iRacing and go to Account...My Account and scroll down the Preferences section.
In the Choose a Content Delivery Network, change that option. If it is currently Limelight, choose Cloudfront (or vice versa), then click the SAVE button and try to update again.
The iRacing.com system software requires access to the internet enabling communication between your computer and the iRacing.com servers. This communication is necessary for operation of the iRacing service; it allows your computer to join online sessions, check for updates to the iRacing software, and it enables other member website functionality.
You may see a blank page or get an error when updating if these executables are blocked by your firewall.
Some common antivirus and firewalls are Norton, AVG, Microsoft Security Essentials, Avast, McAfee, Kaspersky... If you see an error during the next step, or if the update in the next step does not work, it is likely that the problem can be fixed by adding the executable files (listed below)to the list of executables that your firewall allows to communicate over the internet.
Simply disabling the firewall will not automatically allow the necessary program files access to the internet. This has to be accomplished by allowing the following files as exceptions in your particular firewall software. Refer to your firewall instructions or to one of the links below to find the directions for doing so.
Unless you specified otherwise, the default location for your iRacing.com software is your C:\Program Files (x86)\iRacing folder. If you installed it through Steam, then it is located in C:\Program Files (x86)\Steam\steamapps\common\iRacing.
C:\Program Files (x86)\iRacing\iRacingLauncher.exe
C:\Program Files (x86)\iRacing\iRacingLocalServer64.exe
C:\Program Files (x86)\iRacing\iRacingService64.exe
C:\Program Files (x86)\iRacing\iRacingSim64DX11.exe
C:\Program Files (x86)\iRacing\iRacingUpdater.exe
C:\Program Files (x86)\iRacing\UI\iRacingui.exe
Can you also try and go to C:\Program Files(x86)\iRacing\Updater and then right click on the iRacingUpdater and choose Run as Administrator. Then go back to the Members site and refresh (or log in).
One last thing is to turn Windows User Account Control off. You can do this in your Windows Control Panel...Users section.