Brand New Mac Mini drops network after a few minutes

Question

My new Mac Mini (Core Duo) arrived a couple of days back and I couldn't wait to set it up. The next thing I did was to download all the latest updates but the network connection kept dropping after a few minutes (seemingly randomly). This is the wired connection (not airport) and all other computers on the network are working fine.
I thought it might have been a problem with the updates site but now I'm trying to copy my data across the network from my old Windows XP PC (I want to switch) and the connection hangs again after a few minutes.
The only way to get the network back up is to reboot the system, then it works okay for a few more minutes. I've changed the Ethernet cable and the other PCs are working fine - it's just the Mac that has issues.
I wondered if the network card is faulty but does anyone have any other ideas?
I guess as this is only a few days old Apple might exchange it?
</Mark>
Mac Mini Core Duo   Mac OS X (10.4.7)  

Answer 1

Hi John,
My ISP is PlusNet and there are 2 Windows XP PCs, a Windows 2003 Server, 2 Windows 2003 virtual servers, an HP printer, a DLink Wireless Access Point and a Linksys NSLU2 NAS box all working perfectly happily here - the Mac is the only machine that doesn't want to play.
The router only has a single Ethernet port so that's connected to a Netgear 10/100Mbps hub which the other devices use.
In addition it's all NATted so the ISP could only block my external IP address - they don't have access to the router config and in any case all the other devices are communicating with the Internet over the ADSL link with no problems so I think I can rule out the ISP doing anything nasty.
Thanks for the suggestion anyway.
So... here's the progress to date:
I spent two hours on the phone to Apple Support at national rate phone charges. I finally snapped when they asked me to check the firewall settings on my Windows PC (I pointed out that if there was a firewall issue then no data would copy - not several hundred megabytes before timing out). They suggested I took the Mac to an AppleCare centre for diagnosis to see if it could copy files from another Mac (so much for interoperability - they only care that it works with Macs).
I have confirmed that the problem exists on both static IP and DHCP configurations, and whether or not I set the duplex manually or automatically on the network connection. Interestingly it only occurs connected to a 100Mbps/half duplex hub (not a 10/half hub or a 100/full switch or a 100/full crossover cable) but as all the other devices are working fine I can rule out issues withe the hub.
So, now I have the Mac connected to a 100Mbps/full duplex switch, with no other devices connected. That switch has a link to the hub with the other devices connected and on to my ADSL router.
Everything seems to be working but obviously it's not an ideal situation as the Mac should work on the same Ethernet hub as everything else.
Thanks to everyone for their suggestions. If anyone has any further ideas I'd love to hear from you.
Cheers, Mark