This post has been migrated and imported into different systems over the years, I have not had a chance to format this post manually so it may be hard to read but I have left it here as a reference.

I am leaving this mostly as a not for myself and in the hope that it may help someone.

If you have recently installed or updated Airfoil then this may be the cause of your issue as described here.

You could try uninstalling or disabling the Instant On feature of airfoil but if it does not work you can edit the registry directly.

By removing AirfoilInject3.dll from HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft\Windows NT\CurrentVersion\Windows\AppInit_DLLs using regedit you can solve this issue.

This issue has happened to me twice and it has always been a problem with Airfoil. It could also be another program causing this issue such as your antivirus program which you can try disabling temporarily.