Where do the file permissions come into this? It seems like a detail is missing here.
Crashes when invoking context menu shell extensions are generally due to the extensions themselves, and unless they are open source it is difficult/impossible for us to debug them. Reporting the issue to the QuickSFV authors may be the best thing to do.
However, if there is a crash dump created matching the time of the crash, and if you link your account, I can check the dump to verify that the crash is happening within the QuickSFV DLL, in case it isn't. (It probably is, from your description, but there are always other possibilities.)