I'll report to upstream that 7.7 is faulty. But upstream faulty version displays a clear error window. The portable version just disappears.
The details are:
On XP SP3:
KchmViewerPortable 7.7 displays its small logo window and disappears.
7.5 seem to run fine.
7.7 occupies 50% more disk space, compared to 7.5. As if 7.7 has lots of new features, or something.