I've encountered that sort of error a lot. And in my experience, it's usually (if not always) due to trying to load more into video memory than there is video memory available. Unfortunately, FPSC was not programmed to handle this situation gracefully. One way around that is to convert your textures to compressed .dds files. And reduce their resolutions where possible. I've noticed that SO MANY released maps and map packs fail to manage texture storage space efficiently.
Some textures will be more compressible without a noticeable reduction in rendering quality. Some will not as much. For example, a texture that doesn't use any alpha (or uses only 1 bit of alpha) can be compressed to DXT1. .DDS files will also load faster, because that's the native format used by DirectX. Other texture files will have to be converted to uncompressed textures while loading. So even a .jpg will take up more video memory than a compressed .DDS file, even though the .jpg has a smaller file size.
P.S. Also, if your .dds files are not already mipmapped, then the loader will have to take the time to mipmap them while loading. So mipmapping your .dds files will save loading time as well.
Judging what we see is the greatest blinder and self-limiter in the universe.
What we perceive is never reality. It is only a story we tell ourselves based on our current perspective, which has far more to do with our beliefs about ourselves than with anything else.