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Aha. If hitting play from the control does work, than it might indeed be some kind of context problem.

You might check out the Control.BeginInvoke Method (Delegate, Object[]) and EndInvoke methods which:

The delegate is called asynchronously, and this method returns immediately. You can call this method from any thread, even the thread that owns the control's handle. If the control's handle does not exist yet, this method searches up the control's parent chain until it finds a control or form that does have a window handle. If no appropriate handle can be found, BeginInvoke will throw an exception. Exceptions within the delegate method are considered untrapped and will be sent to the application's untrapped exception handler.

Note   The BeginInvoke method calls the specified delegate back on a different thread pool thread. You should not block a thread pool thread for any length of time.

Note   There are four methods on a control that are safe to call from any thread: Invoke, BeginInvoke, EndInvoke, and CreateGraphics. For all other method calls, you should use one of the invoke methods to marshal the call to the control's thread.

Altough I can't say for sure that it is INDEED a context problem, but if it is the BeginInvoke should solve it