Why is youtube acting strange?

Ok, most of you know what youtube is. I find it good for those boring times, and whatnot…but recently it’s been acting strange. When I watch a video, somehow the audio stops, it starts as usual in the beginning then sometime by 20 seconds in it disappears for the rest of the video. I don’t click anything and I have to continuously move the little circle back to the 00:00 mark at the beginning an wait to get the audio back for the missing part.Not for long though…rather to only miss another part and have to go back AGAIN! Does anyone know why this is happening? I haven’t changed any computer settings or anything. I have a windows 7 adn youtube had been working fine before but just recently (2–3 weeks) it started doing this. Does anyone know how I can fix this? thaks so much!