QUOTE(Satine @ Oct 15 2005, 09:50 PM)
Are you singing the vowel with your mouth wide? A lot of people are told to sing y/ee sounds by smiling, but this flattens your tongue, blocks up the pharynx, and pulls the larynx way up (giving you the blocking sensation you mentioned). If this is what you're doing you might want to experiment with mouth positions that are more narrow at the sides, allowing the inside of the mouth to create the y/ee sound.
Hope this isn't too confusing. If it is, let me know and I'll try to clarify.
You are right, I was told to sing with my mouth wide and smiling. The problem is more severe with those higher notes where the voice will sound pulling or pressing.