Hi all,
I am in the same boat as you. It seems that the Broadcom 1GB NIC driver is not included in 5 or U1.
After a long while of messing with PowerCLI and ImageBuilder, it turns out that Dell does not provide the offline-bundle of their ESXi package. Being that we only need to make one change (adding or modifying the NIC for net-bnx2), I decided to use the unsupported ESXI-i Customizer (http://v-front.blogspot.com/p/esxi-customizer.html)
I was told this is the right driver package from Dell support:
https://my.vmware.com/group/vmware/details?downloadGroup=DT-ESXi50-Broadcom-bnx2x-17254v502&productId=229
VMware ESXi 5.0 Driver CD for Broadcom NetXtreme II Network/iSCSI/FCoE Driver Set 1.72.54.v50.2
However, after trying to create my own custom bundle with Image Creator, I was very unsuccessful. Dell does not offer the offline-bundle, so I was pretty much at a loss. I could use the regular one but Dell won't support the software unless it's their image. Either way, this did NOT work in either the VMware provided ISO or the Dell provided ISO.
Using the offline zip file that is found when you unzip this package, only changed one thing:
[Thu 08/02/2012 14:33:50.57] ... old version: 1.72.18.v50.4-1OEM.500.0.0.472560
[Thu 08/02/2012 14:33:50.57] ... new version: 1.72.54.v50.2-1OEM.500.0.0.472560
I burned the ISO and am still getting the "No Network Adapters" issue.
Dell hasn't come out with an image that is updated for the R620, and the drivers that they claim to work do not work.
Anyone come up with a fix for this yet?