Network problems

Google doesn't seem to be able to help too much with this...

First of all, we're on orange broadband which is a nightmare - their dns server spends way too much time not working (well, the belkin router says 'DNS: Fail' a lot).

BUT - Two laptops connected to the router wirelessly get some kind of connection issue. There is one pc connected to the router via ethernet cable, which only has issues when orange dns is down.

Randomly, multiple times a day, the internet will appear to stop working. In both IE and FF error messages are displayed. After a while they also crash, along with other programs that access the internet (msn, last fm, etc). The laptops are able to ping IP's and domains, suggesting DNS is working correctly. Both have AVG antivirus and ZoneAlarm Firewall (both free versions).

The router automatically assigns ip's via DHCP with a lease time of a week (i think).

On my laptop I reinstalled vista but no difference, the other laptop is brand new.

Any ideas?

Thanks.