Also, this has happened suddenly and for no apparent reason
I can't think of anything which has changed on any of the computers.
( WormuIus, Sat 25 Jun 2011, 13:16, archived)

is it wireless?
Could someone be stealing some of your internets? Could explain why it comes and goes intermittently? I dunno. Go ask someone else. Soz.
( Windy Pig I'm naturally quite suspicious about the moon., Sat 25 Jun 2011, 13:40, archived)

microwave / cordless phones on?
change the router channel / password / MAC filter only those four PCs?
( moohalaa, Sat 25 Jun 2011, 13:42, archived)