As I fear that the Java bug #8305072 takes a long a long time to be fixed (it seems complicated to reproduce), I chose to circumvent it by using a [font=courier new]FileDialog[/font] rather than a [font=courier new]JFileChooser[/font] instance in case this error happens (see commit #8910).
Steve confirmed that it fixed his problem. I'll publish a version 7.3 Beta soon with other small changes.