Cloaking email addresses on the web is mandatory these days thanks to the spam vermin out there. Joomla includes a nice content plugin that takes care of this task for you automatically. Unfortunately it also breaks form input values if they contain a pattern that appears to be an email address. The problem is caused by the "catch-all" generic search and replace the plugin does at around line 157 of /plugins/content/emailcloak.php. Here is a quick 'n dirty fix:

Find this (around line 157)

    while (preg_match($pattern, $text, $regs, PREG_OFFSET_CAPTURE)) {
        $mail = $regs[1][0];
        $replacement = JHTML::_('email.cloak', $mail, $mode);

        // Replace the found address with the js cloaked email
        $text = substr_replace($text, $replacement, $regs[1][1], strlen($mail));
    }

.. and replace with this

    $offset = 0;
    while (preg_match($pattern, $text, $regs, PREG_OFFSET_CAPTURE, $offset)) {
        if ($regs[2][0] != '"') {
            $mail = $regs[1][0];
            $replacement = JHTML::_('email.cloak', $mail, $mode);

            // Replace the found address with the js cloaked email
            $text = substr_replace($text, $replacement, $regs[1][1], strlen($mail));

            $offset += strlen($replacement);
        } else {
            $offset = $regs[2][1];
        }
    }

This should keep you safe if you are using double quotes to enclose your tag attributes, i.e., <input type="text" name="email" value="This email address is being protected from spambots. You need JavaScript enabled to view it.">