I get the following error:

doc.createDocumentFragment is not a function
[Break On This Error] fragment = doc.createDocumentFragment();

This is the update function:

jQuery.fn.submitAndUpdate = function() {
    this.submit(function(){
        var params = {};
        $(this).find("input[checked], input[type='text'], input[type='hidden'], input[type='password'], input[type='submit'], option[selected], textarea").filter(":enabled") .each(function() {
            params[ this.name || this.id || this.parentNode.name || this.parentNode.id ] = this.value;
        });
        $.post(this.getAttribute("action") + "?js=true", params, function(data){
            alert(data);
            $(this).html(data); //heres where the error occurs.
        });
        return false;
    });
    return this;
}

This is the data returned in the data variable

Update Successful<br/><form class="mediaForm nohijack" id="mediaForm-377" action="file/update/377" method="post"><div><a class="trackHeader" href="#" id="trackHeader-377">Deep Purple - Deep Purple - 05 - Why Didn´t Rosemary.mp3</a><a title="Deep Purple - Deep Purple - 05 - Why Didn´t Rosemary.mp3" href="track://377">+</a></div><div class="hidden trackInfo" id="trackInfo-377"><label for="AudioFile_track">Track</label><input size="2" maxlength="1" name="AudioFile[track]" id="AudioFile_track" type="text" value="1" /><br><label for="AudioFile_year">Year</label><input size="4" maxlength="4" name="AudioFile[year]" id="AudioFile_year" type="text" value="2001" /><br><label for="AudioFile_title">Title</label><input name="AudioFile[title]" id="AudioFile_title" type="text" maxlength="255" value="Deep Purple - Deep Purple - 05 - Why Didn´t Rosemary.mp3" /><br><label for="AudioFile_album">Album</label><input size="20" name="AudioFile[album]" id="AudioFile_album" type="text" maxlength="255" value="N123one1232312" /><br><label for="AudioFile_artist">Artist</label><input size="20" name="AudioFile[artist]" id="AudioFile_artist" type="text" maxlength="255" value="Non1233e" /><br><label class="error" for="AudioFile_comment">Comment</label><textarea style="width:100%;" rows="2" name="AudioFile[comment]" id="AudioFile_comment" class="error">None123123213qwe213213211323321</textarea><div class="errorMessage">Comment is too long (maximum is 30 characters).</div><br><input class="updateButton" id="updateButton-377" type="submit" name="yt0" value="Update" /></div><script type='text/javascript'>
                $( '#trackInfo-377' ).corner('10px');
                $( '#trackHeader-377' ).click(function(event) {
                    event.preventDefault();
                    $(this).parent().next().slideToggle();
                });

                $( '#mediaForm-377' ).submitAndUpdate();
            </script></form>