Everytime i try to enter 3D mode on any map, I get Error 6: Overflow. I never got this error before. I tried uninstalling and reinstalling. No help. I couldn't find any registry keys to remove. I don't think i changed any of the 3D Mode Settings.
It's failing to enter 3D mode, even on IWAD's that are obviously perfectly built such as DOOM.WAD and DOOM2.WAD.