Tim, The issue may be attributed to the Inventory Collection being enabled during the update. If you could let's disable it, then run the update and reboot, then we can re enable it. You can disable by running the following racadm command - C:\rac>racadm –r xxx.xxx.xxx.xxx –u root –p calvin set LifecycleController.LCAttributes.CollectSystemInventoryOnRestart Disabled Where the xxx.xxx.xxx.xxx is the IP address of the iDRAC on that server. Calvin in this example is the root password. You should receive a confirmation that it modified successfully.  After that you can run the update and it should reboot normally. Then run the same command except for change the value to Enabled. Let me know.
I have found an issue on the R320 that occurs every time I do a BIOS update. From the top: I am using the iDRAC to control the server which is booted up in a Linux environment. I am getting the .BIN file for the BIOS update. I apply the update, and it advances through all the steps normally. At the end, it says something along the lines of "Update Complete, please reboot for changes to take effect" and prompts me to reboot. The issue: When I reboot (immediately when prompted or later,) sometime during the boot process, the iDRAC stops working, and I lose  any remote access to the server. The system never boots unless I go and manually reboot the server, but it boots correctly once I do that, with the update applied. Additional Information: The iDRAC7 firmware and the Lifecycle Controller firmware are updated to the most recent versions.  Why is it hanging during the reboot and making the iDRAC unusable? 
PowerEdge R320 - After BIOS update completes, hangs during reboot. 