I'm having the same problem [I think it is]. And it always happens when I restart a certain beatmap [Cruel Clocks], when I play beatmaps I created myself, and randomly when I am start playing or retrying other beatmaps. If I'm not mistaken, I've been getting it ever since the update where osu changes the options, and it's became more frequent ever since.
I am using a Macbook Pro [Mavericks]. At first I thought it's because osu isn't very compatible with a mac, but then i read this here... FPS: 120, Resolution: 1024 x 786. I don't really play with mods, don't on settings such as hit lightning and combo burst. I don't even on the video. I play CTB. [ btw, err.. sorry if for some reason i am posting out of turn, because this is the first time I am even posting anything on Osu!] I tried updating, turning off all applications besides osu, but it still happens.
System.InvalidOperationException: Begin cannot be called again until End has been successfully called.
at Microsoft.Xna.Framework.Graphics.SpriteBatch.Begin(SpriteBlendMode blendMode, SpriteSortMode sortMode, SaveStateMode stateMode, Matrix transformMatrix)
at Microsoft.Xna.Framework.Graphics.SpriteBatch.Begin(SpriteBlendMode blendMode, SpriteSortMode sortMode, SaveStateMode stateMode)
at #Lm.#sp.#8Fb(Boolean )
at #Lm.#sp.#Ms()
at #Vl.#Yo.#0tb()
at #5i.#4i.#Ms()
at #rb.#xb.#Ms()
at #1h.#0h.#Ms()
at #rb.#xb.#7s()
at #rb.#xb.#it(Object , EventArgs )
at #rb.#Bb.#Dt()
at #rb.#Rb.#Sv(Object , EventArgs )
at System.Windows.Forms.Application.ThreadContext.System.Windows.Forms.UnsafeNativeMethods.IMsoComponent.FDoIdle(Int32 grfidlef)
at System.Windows.Forms.Application.ComponentManager.System.Windows.Forms.UnsafeNativeMethods.IMsoComponentManager.FPushMessageLoop(Int32 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 System.Windows.Forms.Application.Run(Form mainForm)
at #rb.#Rb.#ot()
at #rb.#xb.#ot()
at #1h.#np.#Iwb(String , Boolean )