Profile pictures not displaying in forum
I had also posted my question to my university drupal help list and managed to find an answer.  I don't know how much of this applies to the general community (it may only apply to my specific Drupal install at my university because they include automated configuration adjustments), but here is the solution that worked for me:

My main folder is called simply drupal.  In the file

/drupal/.htaccess

I had changed the line 

Options +FollowSymLinks

to instead read 

Options +SymLinksIfOwnerMatch

The problem was that I had not changed a second copy of this file in another location: 

/drupal/sites/default/files/.htaccess

I made the same changes to this file and now the images show.  I did not simple copy one file to the other location, because the files contain different options and only the one line needed a change.  Again, my drupal install might be unique to my university, but these edits are so minor that I think someone else could try them without getting into too much trouble.  Maybe someone else could lend more insight if needed.