It means that you have an instance of SQL Server that hasn't got a registered ETW event provider. The event provider is implemented incorrectly in SQL Server, so it's not possible for ANTS to detect the real reason there's a problem.
The most likely cause is that the instance is SQL Server Express: Microsoft turned off event tracing in that version, so ANTS can't profile it. The cheapest edition of SQL Server with this feature is the developer edition. You can have both Express and other versions of SQL Server installed, in which case ANTS will profile the other editions but will warn about the Express instance.
If the installer failed to compile the etwcls.mof file for that instance of SQL Server, then you'll also get this error message. You'll find this file in the installation directory for the instance you're interested in (C:\\Program Files\\Microsoft SQL Server\\MSSQL10.SQL2008\\MSSQL\\Binn, for example). You can install it by running 'mofcomp etwcls.mof'.
I think this can also happen if the instance has been renamed at some point in the past. You'll need to edit the .mof file so that the description matches the new instance name (it's at the top, and should be '<instance name> Trace'. The other names don't actually matter.
You can see the installed event providers by running the command 'logman query providers' from an admin command prompt. For any given SQL Server instance that isn't Express, there should be a '<instance name> Trace' entry.
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