I fixed this in version 6.2 by editing /opt/splunk/etc/apps/splunk_app_for_nix/appserver/templates/layout/unix_base.html and changing the reference to jquery-1.6.2.js to jquery-1.8.2.js, which is available from the core Splunk install files under /opt/splunk/share/splunk/search_mrsparkle/exposed/js/contrib/.
Reviewing the Splunk RPM history, it looks like jquery-1.6.2.js was removed somewhere between 6.0.3 and 6.1.1 - I guess if you were upgrading from an older version it would be left there, but for a fresh install it doesn't exist.
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