Actually, I was wondering if it were this Titan IV failure from 1998 (A-20). http://www.fas.org/spp/military/program/launch/titan_iv-20_sum.htm
Nevermind, A-20 was destroyed 40 seconds after liftoff. There was an upper stage failure in 1999 on a Milstar mission. That’s probably it. http://www.spaceflightnow.com/titan/b26/051016history.html