I have the same issue.  it's been happening ever since I upgrade to 64 GB RAM (about a week now).  Funny if they can't handle the RAM.  Running Windows 10 Pro on a Dell XPS 8910.

Last night, the same thing started happening on my laptop. No related software or hardware changes recently.

XPS L521X

Memory : 6 GB

Processor : Intel(R) Core(TM) i5-3230M CPU @ 2.60GHz[Cores 2] [Logical/Core 2]

Operating System : Microsoft Windows 7 Home Premium 

I've been using Advanced SystemCare Pro for several years now on this laptop and my Windows 10 desktop, which essentially does the same thing. So I'll be uninstalling SupportAssist if Dell doesn't fix this soon.

Same issue here.  It runs the Drivers & Downloads successfully.  When it gets to the Hardware Scan, I get the error, "An unexpected error occurred while running this request."  Not a lot of detail on what's causing the error or how to fix it.

Same here, Dell, we've got a problem. (But as I am waiting for a sound driver fix since 2014 I don't think I'll hold my breath.)

Support Assist Client

Same here on my Inspiron 7547. Suddenly about 2 weeks ago I wanted to optimize my system proposed by Dell Assistant and I could run all the other items except " Hardware Scan". It used to work perfectly. 

I too have been getting this error message in SupportAssist for a couple of months now. At first, the program would hang at 97% completion of running Scan Hardware, and I was forced to close it. Now it will not run Scan Hardware at all. It will run the other 4 tests individually without problems. For Scan Hardware, it simply says an unexpected error occurred and the program will close. I am not having any hardware problems or issues that I am aware of, and I keep my PC up to date. I have tried Uninstall/Reinstall of Support Assist without success. I wish Dell would address this issue. From my standpoint, the problem seemed to start around the time of the release of Windows 10 Creators Update in the spring. To add to the misery, SupportAssist keeps dinging me in my Notifications to Optimize My PC, which I cannot do because of this issue. How does one turn off that specific notification?

Equipment: Dell Inspiron 5558 laptop, running Windows 10 Pro, 8 Gb memory, Intel i7-5500 CPU

Exactly same problem. I can run the other tests, cleanup, etc but when I try with the Hardware Test, it gets stuck at 0%  until the error warning appear. And I'm getting mad at getting the "Optimize your PC" notification every time I turn on my laptop. This is really annoying. I just hope and wish Microsoft will fix this issue in the next update. I never had problems with AssistSuport until now. 

Not specifically related to Windows 10 - I'm experiencing the same issue on Windows 7 Home...

I disabled those annoying notifications by turning them off under settings.

Settings > Notifications > i want to receive notifications about hardware and software... (uncheck this box)
I also disabled Scheduled Scans

Settings > Scheduled scans > Enable automated system scans (uncheck this box)

Click "Save"

Thank you TennisAce57. I have done that and it appears to be working. At least, I have not received any of those annoying notifications re:Optimize my PC so far today. Hopefully, Dell will address and fix the Scan Hardware issue in SupportAssist soon, so we can turn our Notifications back on in the future if we want.