If you combine pictures with Hugin, it automatically generate/remove some temporary tif-files in the current folder. Have opened the same folder in XnView, leads to crash it. In my opinion it happens if XnView scans the folder to new files. But the files are handled (create/delete) from Hugin in the same time.

Yesterday I sent a crash report about that problem. Maybe that help, too, to find the bug.
I used XnView MP 0.82 beta 3