Please try the following suggestions:
Log out of iRacing, close browser and open a new browser window.
Reboot your computer.
Run a Registry Cleaner on your machine. There are many free one's out there.
Update Windows to the latest service pack 
Make sure you have the latest version of DirectX Make sure your Cryptographic Service in Windows  is enabled. 
You can find this in your Windows Control Panel...Administrative Tools...Services. 

This can also happen if you have something on your system that is hooking D3D9 and injecting code.
Things like D3D Ripper, procaster, ambBX, iz3d, softTH, may be the cause of this.
Can you please try and identify what it is that is causing the issue and disable it when using iRacing if possible.