Although the 'set -o vi' option works if typed in at at the prompt, it fails to work if included in .bashrc. Moreover if .bashrc includes the line 'set -o vi' setting option vi by hand has no effect. I suspect this is not actually a problem with bash but with a library call that bash uses. As executables which previously worked fine, fail with the 6.0 distribution.
*** This bug has been marked as a duplicate of 2397 ***