There has always been complaints about how YouTube AdSense earnings are represented in the AdSense reports. The issue is, the earnings publishers make from their videos are always delayed and thus do not show up on the daily reports.
The best way to see your YouTube earnings is to go to the payment screen and click on "details." It will open up the details of how you were paid out. Here is a screen capture:

This question was just recently brought up again in the Google AdSense Help forums based on Google announcing they are retiring the old interface.
AdSense engineer, Guillaume, explained:
YouTube earnings are visible in the payment history of the new interface. You should see the same number as in the old interface in one of the two line items on each month, under the "YouTube" label visible after clicking "details".It's difficult to do better, because YouTube earnings are available only on a monthly basis to AdSense, while the new interface is designed for more granular data (daily).
Forum discussion at Google AdSense Help.

Comments:
Zaniia0097
09/30/2011 06:16 pm
how i earn from adsense like u i mean alot of monney plz help any guidline
Anil Gupta
11/16/2011 07:55 am
What is 'Adsense for cotnent- host' signify then? I used to think that it is pointing to YouTube earnings. But, it looks like i was completely wrong!
Daniel Dickey
01/11/2012 07:48 pm
Ya I don't see my youtube anywhere.
Technocator Youtube
02/03/2012 11:35 am
No, actually this will be shown as 'Adsense for Hosted contents'! But only if you are member of Youtube partner program..
Billy Tail
06/29/2012 10:04 pm
AdSense engineer, Guillaume, explained:Something they have never tried as a user because Google AdSence pages show no income, even though YU shows a lot Shown as 'Adsense for Hosted contents'! has nothing