my advice is to see if a dx file by another name has been created and, if so, use that to visualize the field lines.
The full story is below, and might be more interesting to the developers of the apbs plugins. I'm using PyMOL 1.2r3pre and APBS 1.2 with openmpi installed via FINK on OSX 6.2.
The old apbs plugin aborts with the following error:
ObjectMapLoadDXFile-Error: Unable to open file!
ObjectMapLoadDXFile: Does 'pymol-generated.dx' exist?
The file that exists is pymol-generated-PE0.dx. When I change 'Temporary DX file' in the 'Temporary File Locations' tab to pymol-generated-PE0.dx, I get the same error, but now the file that exists is pymol-generated-PE0-PE0.dx (ad infinitum?).
Another problem with the original plugin is that the executables are not found. In my .bashrc I define
In the 'APBS Location', only 'APBS binary location' is set properly. 'APBS psize.py location' is incorrectly set to /sw/share/apbs/tools/manip/psize.py
With the new apbs plugin (APBS Tools2), there's also a problem with the paths. Neither 'APBS binary location' nor 'APBS psize.py location' are set - but the 'pdb2pqr location' is. APBS Tools2 also creates pymol-generated-PE0.dx but is happy to work with it. (In fact, it says 'Could not find pymol-generated.dx so searching for pymol-generated-PE0.dx.') The field lines can be visualized as described by Michael.