Admin->Extension->Extension Installer->JSON.parse

Hello,

I get this error while installing a couple of extensions in admin:

SyntaxError: JSON.parse: unexpected character at line 1 column 1 of the JSON data
OK
<b>Warning</b>: ftp_login(): Sorry, cleartext sessions are not accepted on this server. in <b>/vqmod/vqcache/vq2-admin_controller_extension_installer.php</b> on line <b>295</b>{"error":"Could not login as "}

The FTP settings look fine and is enabled in the settings. Also, I was able to install a few other extension.
Could you please tell me why this could be happening?