i know youtube is changing its html all the time, and parsing it is becoming harder.
One alternative to get youtube info cleanly, from a more stable source is googles own youtube api
http://code.google.com/apis/youtube/2.0/developers_guide_protocol.html
but the real challenge lies in someone making their own json_decode alias. but hell, you could just regex match the json string instead.
heres an example url for one result. and the query = the youtube url
http://gdata.youtube.com/feeds/api/videos?q=http://www.youtube.com/watch?v=Nrm8-vnSEfc&start-index=1&max-results=1&v=2&alt=json
ps: json services are very fast indeed
have phun.