I've tried on various Windows computers:
Windows 10 64 bit (16 GB, SSD): Images load very fast, problem does not occur
Windows 7 32 bit (8 GB, HDD): Problem occurs
Windows XP 32 bit (4 GB, HDD): Problem occurs
Each single file can be loaded without a problem. But when opening the first image and then navigating to the next image, nothing is displayed. Navigation back is not possible.
There is another problem:
If you browse to the folder which contains the large images and
right away double-click on the first image, XnView displays a message box: "File can't be loaded!".

If you navigate to this folder,
wait 5 seconds and then double-click on the first image, XnView displays the first image without problems.
To me this looks as if thumbnail reading/generation prevents opening file.
EDIT:
Szenario B
Some more observations with large files which might help to find out about the problem.
Folder contains four image files:
#1 Large 10.000 x 10.000 pixels, BMP, 100MB
#2 Small image 800 x 800 pixels, JPG
#3 Large 10.000 x 10.000 pixels, BMP, 100MB
#4 Large 10.000 x 10.000 pixels, BMP, 100MB
1. Open the fimage #1
- >Image #1 is displayed (correct)
2. Navigating to next image #2
-> Image #2 is displayed (correct)
3. Navigating to next image #3
-> Image #3 is not displayed (gray, empty image)

4. Navigating to next image #4
-> Image #4 is not displayed (gray, empty image)

5. Navigate back to image #1
-> Image #1 is not displayed (gray, empty image)
Another observation:
The folder which contains the large image files has a folder thumbnail with four miniature images. But the miniatures of the large BMP images are darkened

The miniature of the small image #2 is in normal brightness. (correct).
Szenario C
Previous test with JPG images (also 10.000 x 10.000 pixels, but only 2MB in file size) has no problems.
Folder which contains the JPG images has a folder thumbnail with four miniature images. Miniatures are displayed in correct brightness.