>>28008561) Does it happen with any model? If it takes a specific one, PMX inspect it and fix any issues. Also mind the size/complexity of the model.
2) Does your system have the requirements listed in the ReadMe file of MikuMikuDance? If not, install them.
3) Is your MikuMikuDance version 9.31 or newer? If not, try updating. You could also try using MikuMikuMoving instead.
4) What are your system specifications, including the OS and hardware?
5) Are you running any MMD extensions?
6) Check the program and any relevant libraries in virustotal.
7) Do you happen to have Avast? Might also check the task manager for memory consumption and the time your computer has been running for.
