验证码输入的是正确的，但是提示验证码错误 [ 2.0 版本 ]

验证码输入的是正确的，但是提示验证码错误
控制器

 public function actions() {
        // return external action classes, e.g.:
        return array(
            'captcha' => array(
                'class' => 'CCaptchaAction',
                'backColor' => 0xF1F1F1,
				'fixedVerifyCode' => substr(md5(time()),11,4), //每次都刷新验证码
            ),
        );
    }

代码

<?php if (CCaptcha::checkRequirements()): ?>
                                    <tr>
                                        <td height="25" colspan="2">
                                            <table border="0" cellspacing="0" cellpadding="0">
                                                <tbody>
                                                    <tr>
                                                        <td width="70" height="25" align="right">验证码：</td>
                                                        <td width="75" height="25"><input data-validate="required:验证码不为空" class="in_yz" placeholder=" 验证码" maxlength="4" name="LoginFormMem[verifyCode]" id="LoginFormMem_verifyCode" type="text" /></td>
                                                        <td width="78" height="25" align="center"><?php $this->widget('CCaptcha', array('showRefreshButton' => false, 'clickableImage' => true, 'imageOptions' => array('alt' => '点击换图', 'title' => '点击换图', 'style' => 'cursor:pointer;width:70px;'))); //, array('class'=>'captcha')   ?></td>
                                                    </tr>
                                                </tbody>
                                            </table>
                                        </td>
                                    </tr>
                                <?php endif; ?>

测试地址：首页的登录老是提示验证码错误，然后跳转到会员登录页面在重新输入验证码又正常登录了
http://www.rbzygs.com/