Mac or Windows? If mac then probably a mac issue. I've not had any issues with importing large image files of over 5mb, but I'm on windows. I actually use the .webp image format now though as it's a fraction of the size of png without any noticeable difference in quality.
Hi, what GPU/CPU are you using ? Please update your drivers, especially intel and nvidia. Vis isn't memory intensive at all, but we had some issues with old drivers because we are using non-power-of-two-textures, that old drivers can't handle.
I'll give it a crack as I know vis never seemed memory intensive before. My pc is running really high on its memory usage for no apparent reason. really odd but thanks for the suggestions!