Same here, but only while using bookmarklet and (Shareaholic for Chrome to be specific) and it happens just from time to time while trying to upload a photo (and dissapears if I give a few tries), but always on Youtube (and trying again dosn't help).
Why did the tennis machine get sent back to the repair shop? - SERVER FAIL!
Why was the Subpoena not delivered? - SERVER FAIL!
Why did the customers not get their dinner? - SERVER FAIL!
Why can't I post photos to my soup? - SERVER FAIL!