VS2005 panel with bound controls

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I'm working on someone elses project and there is a form with a panel
control with bound controls bound to a binding source. I want to add
controls to this container and bind some of them to a binding source while
one of the controls will be unbound. Whenever I just add a label (ie modify
the panel via the designer) and run the project in debug mode I get an error
here:
CType(Me.QFeItemsTableAdapter,
System.ComponentModel.ISupportInitialize).BeginInit()
in the form's InitailizeComponent section.
The error says System.Exception:System.Reflection.TargetInvocationException:
Exception has been thrown by the target of an invocation. ---->
System.InvalidCastException: Unable to cast object of type
'MxSellItemMaint.dsSellItemMainTableAdapters.qFeItemsTableAdapter' to
type'System.ComponentModel.ISupportInitialize'.
What could be causing this?

The project with the form is actually a DLL project that runs within another
app if that would cause any of this. As soon as I refetch the latest from
VSS (ie no change) it runs fine in debug mode.