@dkendig said:

Render directly to a VRImage to reduce the amount of memory that the VFB uses to display your rendered output (it can use a TON, especially if you're rendering multiple channels)

+1 - This will usually solve the problem by itself. You can render to EXR, but if you have channels, you need to have ProEXR installed in Photoshop to see the channels.

What are your global Displacement settings?
Have you tried playing with edge length - setting it to 1 or 0.5? (warning! very detailed and slow setting!)