Problem solved. I've learned more about nVidia's Optimus technology in
the last day than I ever wanted to know. The solution, somewhat
ironically, is to ENABLE Optimus in the BIOS, even though the help
text there says only to do so when running Windows. When it's enabled,
the OS sees the Intel integrated graphics as the primary graphics
card, which is fine by me and probably preferable for Qubes. The ACPI
thing was a red herring (a separate and known problem, with a separate
and known solution).
The install went fine and I am indeed writing this very email from my
newly installed Qubes RC1 system. Thanks for all your hard work!
In summary, for the HCL:
Dell Latitude E6520 with i7-2760QM CPU. VT-d works fine (has to be
enabled in BIOS). If you have nVidia graphics you may need to enable
Optimus in BIOS also, even though help text says not to for
non-Windows OSes. (Note that this essentially DISABLES the nVidia GPU
for dom0.)