Windows – What can cause images to not show in HTML Help (chm files) if UAC is Enabled

On a computer running Windows 7 Embedded Standard (SP1), 64 bit, I am not able to view images in any chm files unless UAC is turned completely off.

All of the images are replaced with a small black and white box with an "X" in it.

Things I've tried:

If I transfer the chm files to a different Windows 7 Embedded computer running the exact same version of IE (11.0.9600.18230), the chm files work perfectly, even if UAC is set to "Always Notify".
None of these chm files come from the internet.
No paths to the chm files has a # in it. Even if I copy it to the desktop or C:\ (my user folder is on the D:) I still don't see images.
Internet Explorer is set to display images
There's no "Unblock" button in the properties shown for any chm file
This help file is not on a network drive, and I'm not running Windows XP, but I tried this ItssRestrictions registry fix anyway. I tried setting it to 1, then I set it to the least restrictive setting (4), no effect.
I have tried running regsvr32 to register hhctrl.ocx, itss.dll, and itircl.dll.
If I view the chm file using SumatraPDF, it works perfectly, even as a non-administrator when UAC is enabled.
If I load the help file by running hh.exe from command line as administrator, images work properly. Images don't load if hh is run by a normal user.
If I open the chm file in 7-zip and extract all of the html documents and open them in IE11, the images work even if UAC is enabled.
Internet explorer settings for "Trusted sites" is set to "Low", and I have added "localhost", "127.0.0.1", and the computer's name as trusted sites.
MJ's help report for the working computer
MJ's help report for the non-working computer

Is there anything else I could try to narrow down the possible causes of this problem?

Are there any other security settings that can affect chm files?