I run the latest release of LTPowerCAD on my two PC, on windows 10 64b.
When I try to open a design for example LT8610 or LT8641, it crashes. If I try to open the file directly from the installation folder, I have an error window identical to the screenshots you can find on others topics related with this kind of issue.
I uninstalled SQL server and the simulator, reinstalled it, same problem. I run everything in adminstrator mode. Note that I don't have the problem with some parts, for example LTC7151S, it works well in this case I can open the default solution or a custom old one.
I have this problem on both computers. Looks like recent updates on windows introduced some incompatibilities with your software...because I don't remember having such issues some months ago.