I had the same error. The cause was the table itsec_lockouts of the plugin itheme security. I deleted the locked hosts in the itheme settings, then backup worked.
The file size is about 8GB. Is this a problem for XCloner?
The old version of XCloner had no problem with this file.
The real filename is alevel.zip without 0
I updated manually to 4.6.1 and edited the php.ini adding curl_exec to disable_functions.
No core files were edited and it works now for me.
Are any negative effects to be expected?