I finally found time to complete my changes to the CodeLab implementation of Normal Map Plus. The goal was to fix the edge-line artifacts when the zoom level doesn't show the entire image, but I'm also interested in whether by some chance it fixes the crash. My previous version now crashes on my system, though I made no changes to it since when it worked. Presumably that's due to a Windows update on my computer. So far, my new version doesn't crash for me. Perhaps some change I made happens to avoid the problem (or perhaps not).
I made quite a few changes, and I haven't had time to do a thorough test, so nothing is guaranteed.
For the DLL and the source code, please see the thread : NormalMapPlus (CodeLab Implementation)