Couple things... for one, you should never use a user-supplied e-mail address for the "From" header; doing so is very likely to get you labeled as an open relay and blacklisted by RBL's and the like. Always use a valid e-mail address on your own domain; if you want to incorporate the user's e-mail address, do so in a "Reply-To" header instead.
Also, the line endings on your headers line are reversed: it should be CR LF, not LF CR.
Finally, is display_errors set to On and error_reporting set to E_ALL?