Mac problems

ms_danson has already posted a couple of questions on this problem we are having so this post is directed at those who are not already puzzling over this. (see http://ms-danson.livejournal.com/373055.html and http://ms-danson.livejournal.com/372566.html for related discussion).

We have been (successfully) using Sympatico to access the internet using a DSL modem. The Airport Express, after a bit of nudging, was able to converse happily with the DSL modem. We connected the Airport (our wireless router) to the DSL modem and both home computers (a Mac G5 and a Powerbook) had crunchy internet goodness. All was well but the telephone line is crappy (I can hear the static ever time I use it) so I expect there are a lot of dropped packets.

Along comes Rogers who offers a cable modem with higher speed, more bandwidth, and at a lower cost. We had them come in and hook it up, tested the modem and ethernet cable with our Powerbook and confirmed there was no problem getting internet access; in fact, it ran fine all yesterday afternoon.

We then tried to connect it to the Airport Express which is supposed to support DHCP over most cable modems. After tweaking and nudging, ms_danson worked out the bugs and was able to access the internet over the wireless network through the cable modem. There, however, is one significant issue to resolve: after between 5 minutes and 1 hour we lose connection to the internet. The wireless connection is still active, the Airport lights still indicate a valid IP address (which does not necessarily mean an IP the modem recognizes) and the modem lights seem to indicate that there connection and activity. Resetting the modem and Airport restores the connection.

The question now is: how to we stop the network from losing communication with the Internet? Any suggestions are welcome.