I'm not sure I understand why two frames are necessary. You only have one file, and you are only loading it once. I think your "frame 1.1" and "frame 1.2" do nothing. Here's what I see:

$ load c:/temp/nbo.gz filter "NBO"
The Resolver thinks Gaussian
filtering with ;NBO;
filter MOs: false for "     molecular orbital coefficients "
Mulliken charges found for Model 1
Molecular dipole for model 1 = (2.0E-4, 3.3087997, 1.0976)
Using NBO charges for Model 1
748 natural bond orbitals read
748 molecular orbitals read in model 1

$ isosurface mo1 mo 15
mo1 created with cutoff = 0.05 ; number of isosurfaces = 1
color range -1.0 1.0; mapped data range -1.0 to 1.0
$ isosurface mo2 mo 665
mo2 created with cutoff = 0.05 ; number of isosurfaces = 2
color range -1.0 1.0; mapped data range -1.0 to 1.0
$ show frames all

file["1.1"] = "c:/temp/nbo.gz"
title["1.1"] = ""
name["1.1"] = "E(RB+HF-LYP) = -3122.57031345 A.U."

so there's only one frame.


However, in order to switch from the single orbitals to the donor/acceptor
view forth and back, I am currently reloading the molecule.

You can just say

isosurface delete

to get rid of the current isosurfaces and start again. Certainly no need to reload the file.




--
Robert M. Hanson
Professor of Chemistry
St. Olaf College
1520 St. Olaf Ave.
Northfield, MN 55057
http://www.stolaf.edu/people/hansonr
phone: 507-786-3107


If nature does not answer first what we want,
it is better to take what answer we get.

-- Josiah Willard Gibbs, Lecture XXX, Monday, February 5, 1900