If I understand it correctly, it is probably a low memory error. See here - although this was 'starting' not 'creating' dispVM I think (?):
So, based on Marek's advice and Patrick's eventual successful DispVM generation, you could probably:
a) First try shutting down every VM that is not needed before creation of the DispVM i.e. all of them before this step in dom0:
b) If that doesn't work, try leaving the laptop idle for a period of time before re-trying, since that appears to have worked for Patrick (?)
4GB is not a lot of memory for Qubes. If you have sys-net, sys-firewall, sys-whonix, dom-0 and sys-usb running already, then understandably the system is probably on the verge of dying with a couple more VMs. But yeah, strange if a standard DispVM works.
Qubes should probably be run with 12-16 GB as desirable, with 8GB the bare minimum for normal functional use, even though the docs say 4 GB is okay.