Do you mean the right click itself, or only when the Properties dialog opens?
The dialog is not actually part of Opus, it comes from Windows and Opus just asks for it to be displayed. The result should be the same in Explorer, Opus 11 and Opus 12. But since both the right click menu and the Properties dialog run 3rd party plugins it is possible one is going wrong due to some slight difference in versions (which could come down to something as random as where different versions place their code in memory, if a plugin has a bug that corrupts memory).
Using ShellExView to disable all context menu and property sheet plugins, then rebooting, would be my first suggestion for isolating the cause. If the crash then stops, it implies one of the disabled plugins was involved. More detail on that here: