Hi bmusicus,
I have seen this problem before with a few other customers and have been unable to track this issue down. I have spent several hours searching for a solution to this, and most searches lead me to believe there is some issue with the PC system configuration. I will link the google results for a reasonable search term for this, and you can find this problem across the board for a large number of applications.
The ntdll library which you noted, is the Microsoft Win32 library responsible for the file dialog (among other things).
For other customers with this issue, they have been able to get around it by installing the 32bit version of the software instead of the 64bit version, or vice-versa. Give that a shot, and see if this allows you to save files. http://www.productbundlesdemo.kinsta.cloud/Spike for the latest software.
If you try some of the troubleshooting tips found online for this issue, and find something that works, we would love to hear about it.
I apologize for the inconvenience. Let me know if installing the other version of Spike resolves your issue.
Regards,
A.J.
