After having written a few helper classes in magento, now i have this problem, i'm getting this error

Fatal error: Class 'Zend_Log' not found in app\code\local\Uhma\Program\Helper\Data.php on line 33

in line 33 i have this 

function WBSAPI_OnceProbe ()
{
    return ( $this->WBSAPI_CurlCall ( "once?action=probe" , &$result) );//LINE 33
}

the function i'm calling with the return is this 

function WBSAPI_CurlCall ( $service , &$result=null )
{
    try {
        $s = curl_init();
            curl_setopt($s,CURLOPT_URL,MYWBSAPIURL.$service);
            curl_setopt($s,CURLOPT_POST,false);
            curl_setopt($s, CURLOPT_RETURNTRANSFER, 1);
            $output = curl_exec($s);
            curl_close($s);
        $result = json_decode ( $output , TRUE );
        if (!is_array($result)) return (false);
        if (!key_exists('status',$result)) return (false);
        if ($result['status'] != 0) return (false);

        return ( true );
    } catch ( Exception $e ) {
        return ( false );
    }
}

i've been in google for a while, some say that it is a function in my helper that is overwriting a function from magento's, i put WBSAPI_ to all my functions at the begining, so, it can't be the cause, i keep getting the same error and i dont know what else to try, need some help here

if it can help, i have some other definitioNs in my file, somthing like this 

define ('MYWBSAPIURL','wbsapi.withings.net/');
define ('MYAPIURL','scalews.withings.net/cgi-bin/');

define ('pound',0.453592);
define ('inch', 0.0254);
class Uhma_Program_Helper_Data extends Mage_Core_Helper_Abstract{
    //CLASS CONTENT
}

thanks

php magento
Edit
Report