Did you use XcomUtil on your Steam DOS/Windows Version?
Because XcomUtil makes some crazy patches to a lot of the original files, which is what you want playing the DOS/Windows version.
OpenXcom relies on the original gamefile, which need
NOT to be tempered with by XcomUtil and need to be applied with universal data patch winterheart linked.
This is important and XcomUtil tempered files may result in some very unpredictive behaviour, like CTD's weird crashes etc..
@ OP are you familar with md5 checksums?
I posted the md5 checksums of my gamefiles
here on pastebin (also attached as *.txt) so you can have something to compare, i use the 1.4 DOS Version with a applied Universal Data Patch.
This will allow you to compare your own files against those checksums and lets us find out if your files are ok or have been tempered with.