Is the Mac (or Mac Mini) known to cause issues with certain kinds of
ethernet switching hubs, perhaps when used in conjunction with PCs?

I'm a long (long) time PC user and have a wired network of various PCs
in my home office. I just bought a Mac Mini and set it up here. Things
were working perfectly right out of the box, even to the point of the
Mac finding the network, downloading updates, seeing the Windows
shares and network printers, and working with both of my monitors.

So last night, I started a download of the iPhone SDK (>2GB) and went
to bed. In the morning, I found that the download quit at like 600MB.
Not only that, but the Mac was no longer online. I subsequently found
that some of the other machines had lost contact with each other.

I've narrowed it down to one specific switching hub that has been
behaving itself up to now. The Mac is going through a 3com switch to a
Dlink switch, which seems to be the center of the problem. The Mac can
ping devices on the 3com hub, no problem. But devices on the Dlink,
the next hub out, experience 30% to 90% packet loss. BTW, both
switches, the Mac Mini, and most of the other machines involved are
all gigabit ethernet. The cable scopes out ok with an ethernet tester.

I've rebooted the switches, the Mac (BTW, it's just like a PC in this
regard-- update, reboot, update, reboot, firmware update, reboot; the
more things change, the more they remain the same...). After
disconnecting the Mac from the network, the seemingly bum switch has
settled down and things are humming again...but without the Mac.

Are there any known issues? If not, any more ideas what I should try?

Thanks
tbone