Too Much Ghost Hunters?

'There's somethin weird, in the neighborhood' *singing in the tune of GhostBusters song.* Ok, something is going on and I am not sure what. Here's the scoop. Over the last month, or two, I have been awoken from a 'dead' sleep by a knock on my bedroom window. Let me back up and set the stage.
I live in a first floor apartment. There are about 6 buildings in the complex and my building is the back building, my apartment on the corner. Think of a square, I would be located in the left hand, front corner. More of a rectangle actually but, that's neither here nor there.
3 times now, I have been woken up but a loudish knocking on my bedroom window only to find nothing and no one there. I am not dreaming. Let me qualify that, I was dreaming twice when this occured however it brought me out of my dream and the dreams had nothing to do with my window or my bedroom! It is a very clear, very distinct knock and it is clearly a knocking on the window. Think about it, you know the difference between a knock on wood and a knock on glass right? Yes, you do.
Last night, it happened for the third time. Not only did it happen again but, it was louder and more persistant, if you will. I was dreaming, I was not dreaming a particularly good dream but, it didn't have anything to do with my window, a window, a bedroom or a room for that matter. The knocking always occurs between 3 and 4am. Every time this happens, I wake from a very sound sleep and never see anyone there.
Just so you don't think I am totally 'Mental'..lol My husband was awakened on one occasion as well. He heard the knocking as I did, got up, and checked inside and outside only to find nothing. We both wake/woke immediatly and the window is a large, wide, window so, it would be a bit hard to knock and run without being seen.
Last nights event, being more persistent and seemingly louder, scared the ba-jeebies outta me and I am not ashamed to admit it! I woke instantly, I froze, watching for something, someone, anything to explain what was going on. Nothing. Not a hint of a shadow or movement. I am not sure how long I lay there watching, listening, afraid to move or even breath. Finaly, I told myself that I had to get back to sleep and I began to drift off again, opening my eyes for a few last looks and fell back asleep.
Remembering clearly the events upon the alarm going off, I began to question my sanity. I am watching too much Ghost Hunters? I LOVE that show. Have I opened a door that I shouldn't have and inadvertantly? Is my apartment haunted? Is someone, something, trying to get my attention, to tell me something? Am I hearing things? What is going on? I even went as far as calling the complex manager and asking her if there had been any other reports of this strange knocking and told her what had been happening. She is a 'believer' in the paranormal so, she did not think ok, heres a crazy woman. She was very kind, concerned and understanding.
So, where does this leave me? Sleepless in Indiana? I am not sure at this point. Any thoughts anyone?
Till next time....I'll be watching Ghost Hunters and sleeping as I can. Take care friends and don't let the bed bugs bite!
Mental