mysql_query(): supplied argument is not a valid MySQL-Link

I keep getting some weird errors in this script:
errors:

[B]Warning[/B]:  mysql_connect(): Can't connect to local MySQL server through socket '/var/run/mysqld/mysqld.sock' (2) in [B]/home/www/ikhelper.freehostia.com/globinc/loginfunc.php[/B] on line [B]86[/B]

[B]Warning[/B]:  mysql_select_db(): supplied argument is not a valid MySQL-Link resource in [B]/home/www/ikhelper.freehostia.com/globinc/loginfunc.php[/B] on line [B]87[/B]

[B]Warning[/B]:  mysql_query(): supplied argument is not a valid MySQL-Link resource in [B]/home/www/ikhelper.freehostia.com/globinc/loginfunc.php[/B] on line [B]90[/B]

[B]Warning[/B]:  mysql_num_rows(): supplied argument is not a valid MySQL result resource in [B]/home/www/ikhelper.freehostia.com/globinc/loginfunc.php[/B] on line [B]92[/B]

[B]Warning[/B]:  mysql_query(): supplied argument is not a valid MySQL-Link resource in [B]/home/www/ikhelper.freehostia.com/globinc/loginfunc.php[/B] on line [B]149[/B]

[B]Warning[/B]:  mysql_num_rows(): supplied argument is not a valid MySQL result resource in [B]/home/www/ikhelper.freehostia.com/globinc/loginfunc.php[/B] on line [B]150
[/B]

and the script:

<?php

function show_login_form($username,$password,$regcode)
{
  ?>
  <h1>Login</h1>

  <p>
   Login by typing your username and password into
   the boxes below and clicking on the 'Login' button.
   Your username must match your IK account username <b>exactly</b>
   and the password <b>must be different</b>.
  </p>

  <form action="login.php" method="post">
   <table border=0 cellpadding=0 cellspacing=0>
    <tr>
     <td align="right">Username:
     <Input type=text name=username value="<?echo stripslashes($username)?>" class=textinput>
     </td>
    </tr>

    <tr>
     <td align="right">Password:
      <Input type=password name=password value="" class=textinput>
     </td>
    </tr>

    <tr>
     <td>&nbsp;</td>
    </tr>

    <tr>
     <td align="right">
      <input type=submit name=submit value="Login">
     </td>
    </tr>
   </table>

  <p>
   If you do not have an account, please click <a href="register.php">here</a>
   to register an account, or if you have a registration code, enter it here:
   <input type=text name=regcode size=5 value="<?echo stripslashes($regcode);?>" class=textinput>.
  </p>

  </form>
  <?
}

function prepare_failed_alert($failedattempts)
 {
  if ($failedattempts == 1)
   {
    $string  = "Warning, there has been a failed attempt ";
   }
  else
   {
    $string  = "Warning, there have been $failedattempts failed attempts ";
   }
  $string .= "to log into your account.";

  $_SESSION['head_message'] .= $string;
 }

function process_groups()
 {
    // now we'll get the group memberships
    $groups="groupfileeveryone";

    // set the session variables for the groups you want to check.  If found it will
    // contain a positive number, if not, it will contain FALSE and the existance of 
    // it can be checked with:
    //
    // if ($_SESSION["variable"])
    //
    $_SESSION['group_all']=strpos($groups,"everyone");
 }

function authenticate($username,$password,$regcode)
 {
    require_once ("usersql.php");

    $loginwhere=$_SERVER['REMOTE_ADDR'];
    $loginwhen=date("Y/m/d H:i:s",time());

    $loginconn=mysql_connect($userhost,$useruser,$userpass);
    mysql_select_db($userdb,$loginconn);

    $query="SELECT * FROM $usertable WHERE username='$username' AND password='$password'";
    $result=mysql_query($query,$loginconn);

    if(mysql_num_rows($result))
     {
      $loginrow=mysql_fetch_array($result);
      $failedattempts=$loginrow['failedattempts'];
      $dbregcode=$loginrow['userreqcode'];
      if ($dbregcode=="")
       {
        $query="UPDATE $usertable SET lastloginwhere='$loginwhere', failedattempts='0',
               lastloginwhen='$loginwhen' WHERE username='$username'";
        $result=mysql_query($query,$loginconn);
        $_SESSION['username']=$myrow['username'];

  process_groups();

        if ($failedattempts > 0)
         {
          prepare_failed_alert($failedattempts);
         }

        if ($regcode != "")
         {
          $_SESSION['alert'] .= "You don't need to enter the registration code any more";
         }
        return true;
       } // end if dbregcode is empty
      else
       {
        if ($dbregcode == $regcode)
         {
           $query="UPDATE $usertable SET userreqcode='', lastloginwhere='$loginwhere',
                  active='1', useractivated='$loginwhen', failedattempts='0',
                  lastloginwhen='$loginwhen' WHERE username='$username'";
           $result=mysql_query($query,$loginconn);

          if ($failedattempts > 0)
           {
            prepare_failed_alert($failedattempts);
           } // end failed attempts

           $_SESSION['username']=$myrow['username'];

  process_groups();


           return true;
         } // end if the regcode matched
        else
         {
          $_SESSION['alert'] = "You need to enter the registration code as well";
          return false;
         } // end if the regcode didn't match
       } // end else not empty
     }
    else
     {
      // let's see if the username was valid
      $query="SELECT * FROM $usertable WHERE username='$username'";
      $result=mysql_query($query,$loginconn);
      if(mysql_num_rows($result))
       {
        $loginrow=mysql_fetch_array($result);
        $failedattempts=$loginrow['failedattempts'];
        $failedattempts++;
        $query="UPDATE $usertable SET failedattempts='$failedattempts'
          WHERE username='$username'";
        $result=mysql_query($query,$loginconn);
       } // end if we found a valid username

      $_SESSION['alert'] = "Invalid Username and Password, please try again";
      return false;
     }
 }
?>

whats the problem?

thanks!