ganpat,
i do not have much experience on this, but i would suggest checking your visa for the approved entrance date. i belive when you filled out your application it asked you the date you were planning on entering the country.
on the other hand, im in the US too and sort of in the same situation as yours. i have lots of questions as i get ready to send my visa application off to the canadian embassy in my country. would you mind sending me an email (morenos15@yahoo.com) with the answers to these questions or posting them here?
-country of origin
-type of visa you currently hold/did you ever fall out of status?
-how long did it take for them to approve your app?
-where in canada are you going/school?
-whats your program of study?
thanks.