In Windows 8 Store apps, if a combo box is included inside a popup like a normal fly out, and the selection changed event causes the popup to close, and the App running on ATOM processor machine, then the App will crash most of the times. This issue just happens on ATOM processors.

The ReasonSince there’s a ComboBox inside a popup when the ComboBox’s Selection Changed event fires, the outer popup gets closed. If garbage collection (GC) happens to come in at exactly that point, it exposes a ref count problem (The GC causes the VisualState to go away, but the ComboBox is still on the call stack and wants to use it.)

Temporary fix: Try to change your app logic to avoid closing the popup at the time of selection changed event fired.

This issue was reported to Microsoft
 and a request for a fix has been submitted. They did a hotfix which solved this issue.