Why would Silverlight be crashing in Release but not in Debug mode?

I have a Silverlight App that has worked well in Debug and Release modes for weeks.

It still works well in Debug mode.

However, now when I run it in Release mode, it starts, shows me the screen, loads the data, then hangs, and the browser (Firefox) closes automatically. I've tried other browsers and each of them crashes, Chrome says "The Silverlight Plug-In has crashed" for instance.

Here are the last lines of Output that I get:

'firefox.exe' (Silverlight): Loaded 'System.Windows.Controls'
'firefox.exe' (Silverlight): Loaded 'System.Windows.Controls.Toolkit'
'firefox.exe' (Silverlight): Loaded 'C:\Program Files\Microsoft Silverlight\4.0.50524.0\en-US\mscorlib.debug.resources.dll'
'firefox.exe' (Silverlight): Loaded 'C:\Program Files\Microsoft Silverlight\4.0.50524.0\en-US\System.Windows.debug.resources.dll'
The program '[1120] firefox.exe: Silverlight' has exited with code -2147023895 (0x800703e9).

How can I get more information about what is happening at the point of crash in Release mode that is not happening in Debug mode?

This seems relevant to your issue. From the update at the bottom, it seems that

the display string used for the debugger triggered a program path which was not executed otherwise, and there it entered in an endless loop