What version of the product are you using?
Lattest

Do you have an error log of what happened?
Date: 2009-11-02 13:41:46
ID: 1
Error occured in: Global
Count: 1
Message: ...ibs\LibQuixote-2.0\LibQuixote-2.0\LibQuixote-2.0.lua line 280:
   table index is nil
Debug:
   [C]: ?
   ...ibs\LibQuixote-2.0\LibQuixote-2.0\LibQuixote-2.0.lua:280 QUEST_LOG_UPDATE()
   beql\beql.lua:171 ?()
   ...ibs\LibQuixote-2.0\LibQuixote-2.0\LibQuixote-2.0.lua:115
      ...ibs\LibQuixote-2.0\LibQuixote-2.0\LibQuixote-2.0.lua:114
AddOns:
  Swatter, v5.6.4424 (KangaII)
  AuldLangSyne, v2.0
  AuldLangSyneFriendList, v2.0
  AuldLangSyneNote, v2.0
  Automaton, v1.3.9
  Babylonian, v5.1.DEV.130
  Bartender4, v4.4.1
  BasicMinimap, v1.62
  beql, v1.0.9 Alpha
  BrockerXPStats, v0.1
  BrokerMoney, v1.36
  BrokerRecZone, v3.0.66
  BrokerSysMon, vv1.1
  BrokeruClock, v3.2.2
  ButtonFacade, v3.2.285
  ButtonFacadeCaith, v3.0.2
  Castbars, v
  Configator, v5.1.DEV.190
  DebugLib, v5.1.DEV.130
  DockingStation, v0.3.2 (Beta)
  ElkBuffBars, v2.2.5-150
  GnomishVendorShrinker, v3.2.0.3
  Grid, v1.30200.2009081101
  Informant, v5.6.4424 (KangaII)
  kgPanels, vv1.33
  LightHeaded, v297
  Mapster, v1.2.3
  nDragIt, v2.0-release
  Omen, v3.0.8
  OneBag3, vv3.3.10
  OneBank3, vv3.3.6
  OneRing3, vv3.2.5       
  Parrot, vv1.10.1
  PitBull4, vv4.0.0-beta5
  PitBull4Aggro, vv4.0.0-beta5
  PitBull4Aura, vv4.0.0-beta5
  PitBull4Background, vv4.0.0-beta5
  PitBull4BlankSpace, vv4.0.0-beta5
  PitBull4Border, vv4.0.0-beta5
  PitBull4CastBar, vv4.0.0-beta5
  PitBull4CastBarLatency, vv4.0.0-beta5
  PitBull4CombatFader, vv4.0.0-beta5
  PitBull4CombatIcon, vv4.0.0-beta5
  PitBull4CombatText, vv4.0.0-beta5
  PitBull4ComboPoints, vv4.0.0-beta5
  PitBull4DruidManaBar, vv4.0.0-beta5
  PitBull4ExperienceBar, vv4.0.0-beta5
  PitBull4HealthBar, vv4.0.0-beta5
  PitBull4HideBlizzard, vv4.0.0-beta5
  PitBull4Highlight, vv4.0.0-beta5
  PitBull4HostilityFader, vv4.0.0-beta5
  PitBull4LeaderIcon, vv4.0.0-beta5
  PitBull4LuaTexts, vv4.0.0-beta5
  PitBull4ManaSpark, vv4.0.0-beta5
  PitBull4MasterLooterIcon, vv4.0.0-beta5
  PitBull4Portrait, vv4.0.0-beta5
  PitBull4PowerBar, vv4.0.0-beta5
  PitBull4PvPIcon, vv4.0.0-beta5
  PitBull4RaidTargetIcon, vv4.0.0-beta5
  PitBull4RangeFader, vv4.0.0-beta5
  PitBull4ReadyCheckIcon, vv4.0.0-beta5
  PitBull4ReputationBar, vv4.0.0-beta5
  PitBull4RestIcon, vv4.0.0-beta5
  PitBull4Sounds, vv4.0.0-beta5
  PitBull4ThreatBar, vv4.0.0-beta5
  PitBull4VisualHeal, vv4.0.0-beta5
  PitBull4VoiceIcon, vv4.0.0-beta5
  PowerAuras, v2.6.3I
  Prat30, v3.2.4
  Prat30Libraries, v
  Recount, v
  SharedMedia, v3.0
  SharedMediaAdditionalFonts, v1.0
  SlideBar, v5.6.4424 (KangaII)
  Stubby, v5.6.4424 (KangaII)
  tekKompare, v3.0.3.5
  teksLoot, v3.2.0.7
  TinyTip, v0.3-Beta
  TomTom, v222
  XLoot, v0.9
  BlizRuntimeLib_enUS v3.2.2.30200 <eu>
  (ck=912)

Please provide any additional information below.
Seems to start appearing when i took the quest http://www.wowhead.com/?quest=1380 for some reason ...
After reloging to the game the questtracker is just not working anymore showing only the white square.