Switch and Hub Issues

Hello,
Our company bought new office space which included a number of new switches which were already installed.
We seem to have problems with some people in cubes who use hubs and static IP’s on their multiple Linux (RH7.2) or Windows 2K etc systems. When the reboot, the linux machines will report conflicts of “another machine has this ip address” and will just not work. The Windoze machines work, but seem to drop connection and are also unable to receive pings (can send). Any idea if a protocol that was on these switches could be causing issues? Systems directly connected to switch seem to be okay.

8 Baystack 450T 24Ports stacked.
Intel/Shiva VPN/Firewall w/Nat
Various manufacturer of hubs.

Thanks,
Matt