From Xojo Documentation
Occurs when the supplied information is in an unsupported format. This can happen in many situations, including: using a String expression that cannot be evaluated, a bad Date format or an inaccessible FolderItem path.
You can use a string expression to set the column widths via the ListColumn class or the ColumnWidths property of the ListBox. You can use the percent sign or the "*" symbol, as described in those sections. If you use a character that is not permitted, an UnsupportedFormatException will occur.
The following specification causes an UnsupportedFormatException runtime error:
source = Picture.FromData(file.Data)
Catch err As UnsupportedFormatException
// not a picture