It's not clear that you understand my question.

If you run your program by using the Visual Studio IDE, then you are  
running with the debugger.  The debugger is attached, whether you realize  
it or not.

In other words, without the debugger the error doesn't happen.

Now, all that said, if you are not actually interrupting your program with  
the debugger or otherwise doing something that would be expected and  
normally cause a thread to remain active in preference for another thread  
in your application, then perhaps the error is telling you something  
useful.

Note that an "expected and normal" situation might be, for example, making  
a database query that takes a very long time.  I don't know what sort of  
query this might be, but maybe something that tries to extract all of the  
data from a very large data, for example.

Only you can really decide for sure whether the error is of concern or  
not, since only you can judge whether it's reasonable for your application  
to remain stuck in one thread for a long time.  If it's not okay, then you  
should probably look closer at which threads the debugger is talking about  
and why you can't switch from one to the other within the MDA's time limit.

Pete