The error message is:
The virtual machine could not be changed to the selected monitor layout.
If you just added a monitor to the host computer, you must power off and power on the virtual machine to use that monitor.
The symptom is a black screen in the guest (both windowed and full screen) as soon as the XP login screen should appear. I did not change the monitors on the host (also didn't add, remove or replace one).
I am running VMware Workstation 10.0.3 build-1895310 on Windows 7 x64 with latest service packs and patches applied.