Windows Server Backup MMC is crashing

I'm having a problem with Windows Server Backup. When I want to do anything, I get a window that says:

blbmmc.dll

MMC has detected an error in a snap-in and will unload it

• Report this error to Microsoft, and then shut down MMC
• Unload the snap-in and continue running

If I click the first option, the app crashes. If I click the second option, I get this error:

Unhandled exception in Managed Code Snap-in

FX:{811FD892-5EB4-4E73-A147-F1E079E36C4E}
Object reference not set to an instance of an object.

Exception Type:
System.NullReferenceException

Exception Stack Trace:

at Microsoft.SnapIns.Backup.UI.WindowsBackupNode.HandleException(Exception e)
at System.Windows.Forms.Application.ThreadContext.OnThreadException(Exception t)
at System.Windows.Forms.Control.WndProcException(Exception e)
at System.Windows.Forms.NativeWindow.Callback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)
at System.Windows.Forms.UnsafeNativeMethods.DispatchMessageW(MSG& msg)
at System.Windows.Forms.Application.ComponentManager.System.Windows.Forms.UnsafeNativeMethods.IMsoComponentManager.FPushMessageLoop(IntPtr dwComponentID, Int32 reason, Int32 pvLoopData)
at System.Windows.Forms.Application.ThreadContext.RunMessageLoopInner(Int32 reason, ApplicationContext context)
at System.Windows.Forms.Application.ThreadContext.RunMessageLoop(Int32 reason, ApplicationContext context)
at Microsoft.ManagementConsole.Internal.SnapInMessagePumpProxy.Microsoft.ManagementConsole.Internal.ISnapInMessagePumpProxy.Run()
at Microsoft.ManagementConsole.Internal.ISnapInMessagePumpProxy.Run()
at Microsoft.ManagementConsole.Executive.SnapInThread.OnThreadStart()

I have no idea what this error means. Does anyone know what is the cause of the error?

Thanks in advance