In the prefs or the viewport settings (depending on your version) there is a color management setting for the viewport. This may be set to something weird. It really should be set to Linear. But will often be set to SRGB. or adobe RGB. These can change your lighting or the general darkness of a scene. If you are viewing on a CRT by all means use one of these but who does that these days. Srgb and adobe rgb are ONLY made for CRT and can vary from screen to screen. Linear will also give you more latitude to tweak color in post.
Another problem area is that when you render at something other than 8bits your systems color management may not have the right look up table (LUT) to convert the 16bits your monitor can’t handle to the 8 bits it can and in the process things look a little screwy.
While you found the button to turn off the open gl in the render settings there is another one in the preferences under the edit menu. Turn it off there too.
It may be that your GFX cards open GL just doesn’t jive with the flavor of c4D’s open GL. While there are standards, unfortunately there are a bunch of them – kinda like the 27 versions of HD