Safari and other programs have lost it!

Hi All,
My Macs have developed an odd problem, They just loose the connection sometimes. I have two macs - A Macbook and Mac Mini. Both run off my netgear router and are up to date. Both are running the BETA of Safari, but this happened on the previous versions and on firefox. I also have a pc but it does not affect this...

I am often in three locations, House 1 (Home)- Netgear router - ISP:TalkTalk, House 2 - D-Link Router - ISP:TalkTalk and at Work - 3Com Routers - ISP:Something (Not TalkTalk).

I am wondering if it could be TalkTalk as it also happens at House 2 but not at work.

In safari, it comes up with the message 'You are not connected to the internet'. I usually press enter 10 times and it works again.

After all of that, Any ideas?

Thanks;D

Instead of repeatedly jabbing your return key, next time run the Network Diagnostics (just click the button that comes up in Safari when the "You are not connected to the Internet" message comes up.)

It will display a helpful series of red and green indicators that should help you to identify the source of the problem.