I am using CentOS as a network router. I have squid, dansguardian, and dnsmasq installed.
Mostly works great, but occasionally workstations on the network will timeout when trying connect to anything outside the network on any port. Websites that worked a minute prior will timeout, pop/imap client will timeout or return dns errors. If I restart squid, everything works again. This can happen once a week, once a day or once an hour. Really random.