I'd like to second this bug report. This always occurs in the forest on the way to the magic shop (behind the main city with Laanx's temple) - though clears up in the actual magic shop area... This makes it next to impossible to actually find your way to and from the magic/glyph shop (hope somebody's going the right way and follow them). Also, I found that if I expand the character stats dialog to the size of the screen and deselect it (so it's 50% transparent) the sky appears as a shadow (like in the previous screenshot) - otherwise, other than your character (who is only darkly lit), the screen is completely black - though I may be wrong and the sky may be visible at all times.
I'm using, if it helps:
Debian Lenny, 32bit i386
An ATI Mobility Radeon 9600, with the X.org Radeon (6.9.0) driver.
I tried it with ATI's official FGLRX driver and had no change. However, when I was in the unlit areas, the game continually scrolled:
X out of bounds!
Z out of bounds!
Y out of bounds!
(in that order) until I left the area - repeating the message at least hundreds of times in the half minute or so I was in the forest.
Screenshots:

The "everything is black" problem with visible console output.

Showing what it's actually supposed to look like in the background (staring into the city map) as well as the fact that the sky is lighter (light enough to follow back to town if you're lucky and don't get turned around).
...Now, where can I find some torches to get through this long, dark, night? ...Or at least increase the gamma to... 12...
SOLVED!:A thousand cheers! It appears that after running the updater (even though I downloaded 0.4.0.1 yesterday) fixed the Black (Black, Black, Black, Black, Black, Black) Forest issue! The forest to the magic shop is now textured! (Sadly, it's no longer the "Black x7 Forest"... That should be it's official name.)
Perhaps even the missing textures in the Death Realm (causing a very unnerving HOM) were fixed... Though I'd rather not die and find out, if you didn't mind.