Powershell profile.ps1 cannot be loaded because its operation is blocked by software restriction policies

If I delete or move the problem profile script then all of my PowerShell hosts start without errors, including the PowerShell ISE which was using it's own Current User Current Host script C:\Users\MyUserName\Documents\WindowsPowerShell\Microsoft.PowerShellISE_profile.ps1

It turns out that the problem with my All Hosts profile script was that it was completely…