Any number of reasons. Here are some that we have seen to date:

• DNS misconfigured. DNS lookups are done by MySQL servers before accepting a connection. If the DNS is misconfigured then lookups may have to time-out before the connection is accepted.
• Hosts file misconfigured. Check hosts files on server.
• Client PC not in DNS. Same affect as above. If no DNS is being used then create the appropriate hosts file entries on the server.