It's very likely that you're out of RAM. Typical behavior.
Displacements eat up A LOT and if you have a huge image, like A3 and have the displacement still set to 2px, you'll get very very fine displacements but it will also drastically increase the hunger for memory.
For example, You have an image that is 500*500, the disp. size is 2px and it's detailed enough. If you raise the resolution to 1k*1k, you have an image 4 times larger and if the disp. value is not changed, you might get crisper displacements but the memory amount will also increase by that factor.
If you'd now render the image as 4k², you'll need 64 times the memory compared to the initial 500² resolution.
(Not sure if the values are accurate, it might be a different factor, I just assumed it to be similar to subdivisions)
Anyhow, the higher the resolution, the higher you can go with the screen-space displacement to achieve the same look.
Try what works best and don't enter unnecessary small values.
Switching to unit size(cm) displacement might be the better option for large images.
BTW, it doesn't have to be the displacement in your case. There are other things that also eat a lot of memory. some of the most recent threads are about that topic.
