Run-time error '380': Could not set the ControlSource property. Invalid property value.

Excel and VBA changes it's behavior: first it runs OK, but after a couple of runs it reports: Run-time error '380': Could not set the ControlSource property. Invalid property value. I have to turn excel off and on, then it works for a while again.
The feeling I'm having is VBA does not consider the control as being a control after some hidden property is changed due to I don't know what kind of event, cannot prove.

I wonder somebody could tell me what kind of workaround I can use to neutralize this phenomenon.

In xl2007 there is a UserForm that picks cells content from a row of a sheet and populates texboxes, optionbuttons, whatevers by the following method:

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Another example, using another type of populating strategy, throwing the same run-time error after some ok runs:

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Previously worked aok. Users go back filling the sheet cell by cell. So inefficient, it breaks my heart.

Would appreciate any kind of direction.

I'd recommend you don't use controlsource at all-simply populate the controls in code and write any data back in code.

Can you advise what you mean by populate the controls with code?
What is the event that triggers the data going back on the sheet? Something like Private Sub TextBox1_Change() ?