ETW: Data Collector Set already exists / was not found

I am getting a cool error that I cannot figure out.

I create a LOGMAN trace session:

logman create trace mytrace -p Bluegarden-SalaryApp 0xFFFF -ets

that runs successfully.

Then I try to start it:

logman start mytrace

And I get an error message:

Data Collector Set was not found.

So, I run the create trace again and get:

Data Collector Set already exists.

When I try to start, delete or stop the trace I get:

Data Collector Set was not found.

My PowerShell is running "Run as Administrator".

Any clues?

Eamonn J.