May I suggest that _epic_ is not synonymous with _severe_. Epic suggests scale in both time and place. To me, an epic bug would affect a large number of people over a very long period of time. Perhaps something to do with IE security would be epic by virtue of its world-wide and decade-long impact.

On a smaller scale, epic might describe something that brings an entire company down, perhaps (if you believe some of the rants) the decision to rewrite the Netscape browser from the ground up.

JM2C on "epic"...