Was there any further text available if you expanded the Details section of that error message? You might consider opening up CRAD GUI MAIN.vi and doing a force recompile of all the VIs to make sure there aren't any compilation errors present. You can force recompile a VI by holding down Ctrl and pressing the run arrow. You can force recompile a VI and all of its subVIs down the chain by holding down Ctrl+Shift and pressing the run arrow.
Does doing this break the run arrow?
Jarrod S.
National Instruments