Hi and welcome!
About your problem, a few details would help:
1. Does it happen with regular Doom2?
2. Does it happen with other gameplay mods?
3. How do you launch D4D?
4. How big is your D4D file? Where did you get it from?
"It was like getting something in the daylight that what you see in the night light." -- Thierry Guetta
"There were things from everywhere else." -- Blood Zero Hell
"Wherever you are, I give you this song." -- DBThanatos -- Blessing in Disguise