Development of Creative Commons licenses

[s kemp <spkemp AT panix.com>]

I've heard nothing back on this.  Would someone PLEASE clue me in if I 
am posting in the wrong place? THANK YOU!

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I contribute musical compositions to an internet site that requires
agreeing to, among other Terms and Conditions, the following:

"MATERIALS POSTED BY VISITORS

BY POSTING, SUBMITTING, LINKING, UPLOADING OR OTHERWISE SENDING ANY
MATERIALS INCLUDING BUT NOT LIMITED TO IMAGES, AUDIO FILES, VIDEO FILES,
TEXT FILES, AND ALL WORKS OF AUTHORSHIP ("CONTRIBUTIONS") TO US OR TO
THE ****** WEB SITE, YOU WARRANT THAT YOU OWN ALL NECESSARY RIGHTS (OR
WARRANT THAT THE OWNER OF SUCH RIGHTS HAS EXPRESSLY GRANTED SUCH RIGHTS
TO YOU OR TO ******) TO POST, SUBMIT, LINK, UPLOAD, OR OTHERWISE SEND
ANY SUCH MATERIAL AND YOU ALSO GRANT TO ****** AND ITS AFFILIATES A
WORLDWIDE, PERPETUAL, IRREVOCABLE, ROYALTY-FREE, NON-EXCLUSIVE LICENSE
TO USE, COPY, PUBLISH, DISPLAY, PERFORM, AND DISTRIBUTE SUCH
CONTRIBUTION ON THE ****** WEBSITE OR ANY MUSIC RELATED WEBSITE OWNED BY
****** OR ITS PARENT OR AFFILIATED COMPANIES."

After agreeing to this and subsequently uploading a song, a set of
Creative Commons licenses is presented in a pick list of options for
Creative Commons licensing (attribution, commercial use and so on)

My question is:

"Do the Creative Commons licenses actually protect my work after having
agreed to the Terms and Conditions clause above?"

Thank you.

S. Kemp