When I open iTunes it plays for an hour or so then stops. It is not frozen as I can click songs and it changes but it does not play. Tried repair still doing the same thing.

I have used iTunes for years on a windows machine. On this particular machine I have had it for 4yrs, windows is up to date, Itunes is up to date. I can open iTunes once and it plays for an hour or so then it stops playback. iTunes is not frozen I can click to different songs and the highlight bar moves to the song but it will not play. The interface looks like it should be playing but it is not. I close iTunes but then I can not reopen it with out rebooting my machine. I went to the iTunes download and ran the repair option and still doing the same thing. I will be deleting and reinstalling next. The only thing I have done recently that I do not always do is sync my iPod. It is functioning normally though. Thoughts on what is going on....