Password REGEX with min 6 chars, at least one letter and one number and may contain special characters

I need a regular expression with condition:

• min 6 characters, max 50 characters
• must contain 1 letter
• must contain 1 number
• may contain special characters like !@#$%^&*()_+

Currently I have pattern: (?!^[0-9]*$)(?!^[a-zA-Z]*$)^([a-zA-Z0-9]{6,50})$

However it doesn't allow special characters, does anybody have a good regex for that?

Thanks

Perhaps a single regex could be used, but that makes it hard to give the user feedback for which rule they aren't following. A more traditional approach like this gives you feedback that you can use in the UI to tell the user what pwd rule is not being met:

function checkPwd(str) {
    if (str.length < 6) {
        return("too_short");
    } else if (str.length > 50) {
        return("too_long");
    } else if (str.search(/\d/) == -1) {
        return("no_num");
    } else if (str.search(/[a-zA-Z]/) == -1) {
        return("no_letter");
    } else if (str.search(/[^a-zA-Z0-9\!\@\#\$\%\^\&\*\(\)\_\+]/) != -1) {
        return("bad_char");
    }
    return("ok");
}

following jfriend00 answer i wrote this fiddle to test his solution with some little changes to make it more visual:

http://jsfiddle.net/9RB49/1/

and this is the code:

checkPwd = function() {
    var str = document.getElementById('pass').value;
    if (str.length < 6) {
        alert("too_short");
        return("too_short");
    } else if (str.length > 50) {
        alert("too_long");
        return("too_long");
    } else if (str.search(/\d/) == -1) {
        alert("no_num");
        return("no_num");
    } else if (str.search(/[a-zA-Z]/) == -1) {
        alert("no_letter");
        return("no_letter");
    } else if (str.search(/[^a-zA-Z0-9\!\@\#\$\%\^\&\*\(\)\_\+\.\,\;\:]/) != -1) {
        alert("bad_char");
        return("bad_char");
    }
    alert("oukey!!");
    return("ok");
}

btw, its working like a charm! ;)

best regards and thanks to jfriend00 of course!