i had a look at this and was getting the same 404, but what i noticed was if you click underneath the player and change it from low resolution to higher resolution video, they will play, its only the low resolution that give out this error...
http://www.guitartricks.com/lesson.php?input=11792&hrv=yes

if this is the video you are meaning that is... if so, just click on the "I prefer High Resolution Video (better quality)." radio button...
hope that helps
:-)