What steps will reproduce the problem?
1. Pick up the alliance-only quest Weaken the Ramparts, a dungeon quest picked up in Honor Hold.

What is the expected output? What do you see instead?
This is due to a blizzard problem.  This quest's header is not showing up, and thus is coming back nil.  LibQuixote tries to use that as a table index, resulting in an error:

What version of the product are you using?
r89-Alpha, although the problem exists in r74-Beta as well.

Do you have an error log of what happened?
Date: 2010-10-15 23:25:33
ID: 1
Error occured in: Global
Count: 1
Message: ...Ons\LibQuixote-2.0\LibQuixote-2.0\LibQuixote-2.0.lua line 247:
   table index is nil
Debug:
   [C]: ?
   ...Ons\LibQuixote-2.0\LibQuixote-2.0\LibQuixote-2.0.lua:247 ?()
   ...Ons\LibQuixote-2.0\LibQuixote-2.0\LibQuixote-2.0.lua:115
      ...Ons\LibQuixote-2.0\LibQuixote-2.0\LibQuixote-2.0.lua:114