Hmm, so I have a slightly wierd dosbox 0.74 setup, which means I don't load ems in dosbox, and instead load emm386 (the dos 6.2 ems controller) via qemm's (another memory manager) device.com (which means i can load, the traditionally in the config.sys, himem.sys in autoexec)...
Anyway, the gist is that I dont use dosbox's ems controller.
with that wc3 works fine (if cycles set to 7000) if VERY slowly. wc4 will play the video okay but crashes out to command prompt with exception 14 (the one dosbox's ems causes) which is wierd.
SO i re-ran wc3demo and wc4demo on my dosbox 0.72 install and both worked fine at 7000 cycles (again slowly) and with ems=false. In practice though, it seems to be simply completing the speed test that needs cycles of 7000.
I certainly cannot find any reason why the max_tree files error appears. However, I attach my dosbox 0.72 config file and my dosbox 0.73 (which is more like 0.74's)
note that the wc4demo video is very laggy, no matter what I do, very bizarre