(followup to self)

the text at Mozilla.org is:

 If Firefox 0.9 is placed in a location with limited access privileges, it
 should be run by a user with access to that location first, so that all
 initial startup files are generated. There may be issues still where if a
 restricted-access user is the first to run the app, these files may not be
 generated properly and Firefox may enter an infinite restart loop. This
 will be fixed in a future release.

This is what I didn't do.

-george