This is not an error specific for SQyog, I believe. Any client running on same system as SQlyog would face the same issue. What happened on the server is something that the hosting support should reply to IMO. One possible reason could be that “skip_name_resolve” setting was changed on the server.
Relevant MySQ documentaton: http://dev.mysql.com/doc/refman/5.6/en/host-cache.html