Changing the install directory to a small name fixed the mission crash issue for me. I remember older versions of Windows used to have problems with long directory names or special characters in the names. I uninstalled the game, created a new set of folders right on C: called games/WH40k CG and reinstalled the game there. I was able to launch the mission after that. I have not played yet so will see it stuttering or other issues exist.

FOR THE EMPEROR!!

Game still crashes very disappointing

3 years on, this stupid bloody bug is still here...

Probably GOG has no access to the source codes or they would've fixed this.

Well I was able to launch the mission but the game freezes when in the combat zone. The characters won't move or do anything. Unplayable in standard Windows 10.

Same here. CTD Fix worked, but now its like the mouse cursor doesnt work. Space marines and a few buttons are clickable, but no commands and no scrolling.

ok, cuting and pasting the entire game folder directly to GoG Galaxy folder, and this one directly to Disc D: worked... but how is that permanent solution working? it is being 5 years and a half since this reply and I still had to do the improvised solution to deal with it...

Thanks for heads up. I am going to play Chaos Gate next, so the information was very useful for me, despite it was a necropost.

chaos gate?

is that the one where orcs can shoot your heads of from miles away.... never had any trouble with playing it... also never managed to get past that first hurdle ;-) ... would recommend btw, if only for the nice challenge

EDIT:

My Previous post was wrong still caused crashes eventually. Applies these fixes and stable now.

Credit to: www.pcgamingwiki.com/wiki/Warhammer_40,000:_Chaos_Gate#Crash_to_desktop_on_Chaos_turn

I.
Game crashes on startup • Link
Comptability mode[citation needed]
Enable the following compatibility settings for WH40K.exe located in <path-to-game>.

Compatibility mode Windows XP (Service Pack 2)
Run in 256 colors (XP/Vista/7)
Disable visual themes (XP/Vista/7)
Disable desktop composition (XP/Vista/7)
Disable display scaling on high DPI settings
Run this program as an administrator

II.
Crash to desktop on Chaos turn • Link
Editing WeapDef.dat[citation needed]
Make a backup of the WeapDef.dat file before editing.
Go to <path-to-game>\Data\
Open WeapDef.dat with a text editor.
Go to line 201 and change PlazPistHit.wav to PlazpistHit.wav.
Save changes.
If the crashing persists change the following lines as well
Go to line 165 and change 4 #Animation to 5 #Animation.
Go to line 200 and change 2 #Number of Sound Effects for Firing to 1 #Number of Sound Effects for Firing.