This has been resolved and everyone should be able to run Dell Update now. If anyone is still having this issue, please Restart Dell Client Management services and then reinstall Dell Update.With that said, if you're still having any trouble with this, please use Get Help Now (located on the bottom right of this page) to contact our team. 
I was experiencing some weird behavior from my laptop that hinted at a need for a driver or BIOS update and went to Dell Command Update to address. Unfortunately, I got the "Unable to retrieve system inventory information" error. So I uninstalled (completely and using Revo) the program and reinstalled the most current version. However, the problem persists. The online driver scan on the Dell support page also does not work anymore either. I have restarted the laptop several times. Nothing seems to work. 
Dell Command Update v5 Unable to retrieve System inventor information