I'm having a similar problem.
When starting the game, i get this error message:
java.lang.NullPointerException
at forge.quest.QuestController.getDeckConstructionRules(QuestController.java:617)
at forge.quest.QuestController.resetDuelsManager(QuestController.java:440)
at forge.quest.QuestController.getDuelsManager(QuestController.java:413)
at forge.deck.DeckProxy.getAllQuestEventAndChallenges(DeckProxy.java:523)
at forge.deckchooser.FDeckChooser.updateQuestEvents(FDeckChooser.java:236)
at forge.deckchooser.FDeckChooser.refreshDecksList(FDeckChooser.java:402)
at forge.deckchooser.FDeckChooser.restoreSavedState(FDeckChooser.java:470)
at forge.deckchooser.FDeckChooser.populate(FDeckChooser.java:281)
at forge.screens.home.CLobby.initialize(CLobby.java:75)
at forge.screens.home.sanctioned.CSubmenuConstructed.initialize(CSubmenuConstructed.java:44)
at forge.view.FView.initialize(FView.java:125)
at forge.control.FControl$3.run(FControl.java:268)
at java.awt.event.InvocationEvent.dispatch(Unknown Source)
at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
at java.awt.EventQueue.access$500(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue.dispatchEvent(Unknown Source)
at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.run(Unknown Source)
How did you fixed yours? What do you mean by deleting "userdir"?