I have tried both downloading the drivers and updating as well as downloading IBM's 5.1 version with the same results. I am guessing anyone can recreate this problem on any hardware.
1. Take a machine with two identical NICs, connect each NIC to a separate, non-stacked switch.
2. Connect at least one switch to a network where a DHCP address can be obtained. (No fancy networking, VLANs, or anything else of that nature. Absolutely no configuration on the physical switches. For simplicity, only have one switch connected to a live network, other switch is just simply powered on.)
3. Perform a clean install of ESXi 5.0.
4. Do not change any values when you install, other than your install location if necessary.
5. When your ESXi installation finishes and reboots, go into the console and connect both NICs to the Management network
6. Reboot.
7. When your ESXi host comes back up, you should get a DHCP address and be able to ping the host and from the host as well as connect with the client.
Repeat steps these steps, with 5.1. Does anyone get a DCHP address or any type of communication?