internet connection problem

hi

i've been running a mac and pc with a belkin network since november, without any problems at all,

just lately my internet connection intermittently started to fail
i.e. "cannot find server"

when i do a reboot unplug etc etc the green light on the belkin router
stabilises and the connection comes back - without making any changes
within osx

the mac is the main computer and the pc is a back up sharing a broadband
ethernet connection via wireless router

when this happens it knocks out the internet completely because when i
re plug the cables to just the modem and the mac - the connection is also
gone ( until i unplug reboot etc)

is there something going on in the mac to make this happen?

is there a hardware problem with the router?

my service provider got me back a connection once but the first thing they do is tell me to unplug the router as they dont support it.

belkin made me do reboots and stuff and the connection came back.

this is most annoying and would appreciate some help if anyone can
get back to me

kind regards