Opening Task Manager Slows PC to Crawl - Windows 10 Pro 1709

I have the same issue: a crawling laptop after starting the task manager. Using Firefox and Webroot too. Using windows 10 and FCU since yesterday. A while ago I already disabled the identity protection in WR. Just to be sure I 'allowed' Firefox in WR. Nothing helps in my case.

What I do when this happens is putting my Dell laptop in Hibernation. That going into hibernation is somewhat slower as well. Then, when starting the laptop out of hibernation, there is enough 'responsive time' to kill the task manager or save some result of other applications.

__ edit: Forgot to mention that my hibernate button is the power button. The only key that seems to be responsive when the keyboard is not.

I did this and it worked for maybe a few days and the issue came right back. So disabling powershell was not a permanent fix for me.

After testing, this appears to only permanently fix google chrome being simultaneously with task manager.  I did not reboot; however, i did restart explorer (Rebooting would accomplish this too).

After ScottDobert's solution it seemed the issue was fixed however it has come back yet again.

Same issue intermittently since Win10 Creators Update. Happens to my PC when Task Manager is open at the same time as a browser.

Chrome and Firefox are affected (... but not Edge?).  Task Manager stops responding. Mouse responses lag by several seconds. ditto keyboard. CPU and memory to spare as far as I can tell.

Only happens when browser is open. Disabling Chrome extensions and setting Chrome not to run extensions in background doesn't cure the problem. Problem doesn't arise with 3rd party Task Manager alternative (System Explorer).

If left open long enough in unresponsive state, Task Manager eventually starts responding, and mouse control returns. In my case, the issue then went away for a few weeks until today, when I had reason to reinstall Chrome from scratch. Now it's back.

Uninstalled Chrome and switched to existing Firefox browser. Same deal.

Tomorrow I'll try the wait and see approach with Firefox and report back.

My PC is Dell Inspiron, AMD Phenom II 2600 Mhz with 8 GB of RAM. Also runs Webroot AV.

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Update - 2 hours later. Confirmed that issue is triggered by having Firefox and TM open at same time. All it takes is 2-3 clicks on TM (e.g. switching tab or from programme-name to CPU column) to cause TM to stop responding, then mouse/keyboard responses to lag until PC becomes uncontrollable.

Lag makes closing Firefox almost impossible but when I eventually succeeded in doing so, TM started responding again and HID control returned immediately. 

TM does not break PC when Edge is open.

For the time being I've disabled TM via the group policy editor and will use a 3rd party utility that doesn't conflict with Firefox/Chrome.

Describes the problem I'm having perfectly. Wow, it is March and that was December and this is still and issue.... wow.

Are you using Webroot as your AV?  If so, have you tried "allowing" rather than "protecting" Firefox and Chrome in Webroot's Identity Protection module?  After doing so, you have to shut down Webroot and then re-enable it for the workaround to take effect.  Also, every time Firefox has an update, it gets "protected" again by Webroot and you have to repeat.