This is a grid editor bug.
The reason is simple but the effect seems horrible
That happens while modifying data on grids. If you notice a grid cell has a red border that means "entered value not accepted". You can save or close the screen while grid is in error state but it will crash as soon as you display that screen again.
There are two things to avoid.
1. While editing data do not move to other cells with mouse click. Just press enter.
2. Do not clear numeric values with delete key. Enter zero instead.
The bug is: when grid is in error state, second attempt to display data crashes it. It should simply allow refresh when it is in error state.
Since that grid is part of .net framework library we can't fix the bug because it is closed source.
So it submitted to Microsoft but still not solved.
https://connect.microsoft.com/VisualStudio/feedback/details/532494/wpf-datagrid-and-tabcontrol-deferrefresh-exceptionI didn't tested it with latest (4.5) framework. If it still not solved I'll try to find a workaround.
It will be awesome if .net framework completely becomes open source... It will happen one day but nobody can know when.