Hi,
Actually I've this problem, even if uninstalling and reinstalling:

MagicExceptionType: MagicException
Severity: Fatal
Message: Sorry, an unexpected error has occurred.
ActionToTake: The application will now close.
ExtraDetails:
InternalDetails: The task 'Initializing card data' failed to complete.
in WotC.MtGO.Client.Model.Core.TaskManager.<>cDisplayClass28_0.<RaiseCompletedEvent>b0(Object <p0>) in C:\CM\workspace\releasenext\source\windows\clients\Shiny\Model\WotC.MtGO.Client.Model.Core\TaskManager.cs:riga 339
in System.Windows.Threading.ExceptionWrapper.InternalRealCall(Delegate callback, Object args, Int32 numArgs)
in System.Windows.Threading.ExceptionWrapper.TryCatchWhen(Object source, Delegate callback, Object args, Int32 numArgs, Delegate catchHandler)
in System.Windows.Threading.DispatcherOperation.InvokeImpl()
in System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
in System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
in System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
in MS.Internal.CulturePreservingExecutionContext.Run(CulturePreservingExecutionContext executionContext, ContextCallback callback, Object state)
in System.Windows.Threading.DispatcherOperation.Invoke()
in System.Windows.Threading.Dispatcher.ProcessQueue()
in System.Windows.Threading.Dispatcher.WndProcHook(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled)
in MS.Win32.HwndWrapper.WndProc(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled)
in MS.Win32.HwndSubclass.DispatcherCallbackOperation(Object o)
in System.Windows.Threading.ExceptionWrapper.InternalRealCall(Delegate callback, Object args, Int32 numArgs)
in System.Windows.Threading.ExceptionWrapper.TryCatchWhen(Object source, Delegate callback, Object args, Int32 numArgs, Delegate catchHandler)
in System.Windows.Threading.Dispatcher.LegacyInvokeImpl(DispatcherPriority priority, TimeSpan timeout, Delegate method, Object args, Int32 numArgs)
in MS.Win32.HwndSubclass.SubclassWndProc(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam)
in MS.Win32.UnsafeNativeMethods.DispatchMessage(MSG& msg)
in MS.Win32.UnsafeNativeMethods.DispatchMessage(MSG& msg)
in System.Windows.Threading.Dispatcher.PushFrameImpl(DispatcherFrame frame)
in System.Windows.Application.RunDispatcher(Object ignore)
in System.Windows.Application.RunInternal(Window window)
in Shiny.App.Main() in C:\CM\workspace\releasenext\source\windows\clients\Shiny\View\MainNavigation\obj\Release\App.g.cs:riga 52

Inner exception:MagicExceptionType: CardDataException
Severity: Fatal
Message: There is a critical error.
ActionToTake: The application will now close.
ExtraDetails:
InternalDetails: Error reading XML card data. This usually means that you have a corrupted install folder or registry. Please uninstall MTGO from the add/remove programs menu, and then reinstall the application from the MTGO website.
in WotC.MtGO.Client.Model.Core.CardDataManager.DoInitialize() in C:\CM\workspace\releasenext\source\windows\clients\Shiny\Model\WotC.MtGO.Client.Model.Core\CardDataManager.cs:riga 1524
in WotC.MtGO.Client.Model.Core.LongRunningTask.TaskThread(Object state) in C:\CM\workspace\releasenext\source\windows\clients\Shiny\Model\WotC.MtGO.Client.Model.Core\LongRunningTask.cs:riga 310
in System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
in System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
in System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
in System.Threading.ThreadHelper.ThreadStart(Object obj)

Inner exception:MagicExceptionType: CardDataException
Severity: Fatal
Message: There is a critical error.
ActionToTake: The application will now close.
ExtraDetails:
InternalDetails: Assertion failed: Card data not found at 'C:\Users\Casa\AppData\Local\Apps\2.0\QKYE7PMP.DBB\H3G258PH.H66\mtgo..tion80e21eca2a0e12580003.00044eccf4d447d04458\CardDataSource\MTGOV3CardData.xml'.
in WotC.MtGO.Client.Model.Core.CardDataManager.ResolveCardDataPaths() in C:\CM\workspace\releasenext\source\windows\clients\Shiny\Model\WotC.MtGO.Client.Model.Core\CardDataManager.cs:riga 1422
in WotC.MtGO.Client.Model.Core.CardDataManager.DoInitialize() in C:\CM\workspace\releasenext\source\windows\clients\Shiny\Model\WotC.MtGO.Client.Model.Core\CardDataManager.cs:riga 1524
in WotC.MtGO.Client.Model.Core.LongRunningTask.TaskThread(Object state) in C:\CM\workspace\releasenext\source\windows\clients\Shiny\Model\WotC.MtGO.Client.Model.Core\LongRunningTask.cs:riga 310
in System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
in System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
in System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
in System.Threading.ThreadHelper.ThreadStart(Object obj)

I have had a gamebreaking bug twice now in the commander phantom draft league. One while I was casting Dargo from command zone and Once while an opponent was. The first time it looped for a while and since I was the active player I lost due to inactivity since it was using my time. Fine whatever the table got points and could vote. The second time Just occurred. I had lethal for the table, an opponent portent of betrayaled one of my commanders, swung with it and then tried to sacrifice it to dargo but did not have the mana to finish paying for dargo. This then caused a bug that looped the game for about 15-20 minutes, The game then attempted to restart, we sat in lobby chatting for a few the game crashed again and then we were presented with a proper new game. The active player could not take any actions and we were whittled down again on time. This time once the player lost due to the effect the entire round was ended and it was called a draw where all of us received -1 points and none of us could vote.