Yes, it uses VC as a base but it does go in the Warband Modules.
If this this error occurs again when you are playing go into the "Notes" menu and then "Recent Messages" to see if the actual opcode error is listed. If the game crashes you won't be able to see this though. I fought several battles with masterless men to test to see if an error was forthcoming and didn't see anything. I wonder if ordering the retreat caused the crash?
Thanks for the info about the RGL error. Can you check your rgl_log.txt in Warband to give me more information about what the opcode is? I will take a look into it. I haven't personally seen this problem in my testing but I will check it out. As far as the helms go, I changed the flags on a few of them because of clipping issues with beards.
Have you tried the new version?
I think this mod uses Viking Conquest as its base.