I had always advocated having many browsers in one's computer. When I have some problems, my instinct is to try to solve the problem by using a different browser. Recently, I have been having problems with Youtube videos which either was playing very erratically or just refused to play. When that happened, I switch to another browser, and walla, the video played with no problem.
Just after publishing the above, I went over to the Archie's video You are my candy girl using the Chrome browser. The video played nicely but there was no sound. So I switched to Firefox browser and the video played fine with sound. Why? Don't know but switching browser solved the problem again.