Alessio D'Annibale's questions

I have a debian server with plesk panel, this server is used for a wordpress mu installation with 10k blogs, from apache status I see a unexplained behavior, the same server send 5/10 GET continuous requests (5/10 every second) to root url of some blogs, this is example of access_log apache

lhost.serverhost.eu - - [30/Jul/2012:22:43:58 +0200] "GET / HTTP/1.0" 200 49152 "-" "WordPress/2.9.2; http: subdomainblog .maindomain. it"

I must restart apache to solve the problem, but after a few minutes the problem reappears again. I verified my crontab and there is not a problem

nb: the requests are coming from himself

I have a domain name set with wildcard for all subdomain (*.mydomain.com), I need of exclude a specific subdomain from this condition, I use a record dns for set wildcard and if I set a new record A for a specific subdomain it not work