In 6.0.3.3, opening the quest log (actually pressing M for map, which shows the Jamba quest bar with it) and pressing the "Select" button on the Jamba quest bar throws an error:
Code:
Message: Interface\AddOns\Jamba-Quest\JambaQuest.lua:2149: attempt to index global 'QuestLogDetailScrollFrame' (a nil value)
Time: 11/20/14 19:32:27
Count: 1
Stack: Interface\AddOns\Auctionator\AtrErrorInspector.lua:106: in function <Interface\AddOns\Auctionator\AtrErrorInspector.lua:51>
(tail call): ?
Interface\AddOns\Jamba-Quest\JambaQuest.lua:2149: in function `UpdateQuestLog'
Interface\AddOns\Jamba-Quest\JambaQuest.lua:2208: in function `DoSelectQuestLogEntry'
Interface\AddOns\Jamba-Quest\JambaQuest.lua:2340: in function `JambaOnCommandReceived'
Interface\AddOns\Jamba\JambaCore.lua:360: in function `OnCommandReceived'
Interface\AddOns\Jamba\JambaCommunications.lua:427: in function `?'
...que\libs\CallbackHandler-1.0\CallbackHandler-1.0.lua:147: in function <...que\libs\CallbackHandler-1.0\CallbackHandler-1.0.lua:147>
[string "safecall Dispatcher[4]"]:4: in function <[string "safecall Dispatcher[4]"]:4>
[C]: ?
[string "safecall Dispatcher[4]"]:13: in function `?'
...que\libs\CallbackHandler-1.0\CallbackHandler-1.0.lua:92: in function `Fire'
...erface\AddOns\Jamba\Libs\AceComm-3.0\AceComm-3.0.lua:261: in function <...erface\AddOns\Jamba\Libs\AceComm-3.0\AceComm-3.0.lua:243>

Locals: <none>
[edit] Same error when trying to abandon a quest.