Lost access to help system, ArcMap, 10.5

[FelixPertziger]

Today I found that I can't access help on any system tool when I click <Tool Help> button. It says (see attachment):

Can’t reach this page

Make sure the web address //ieframe.dll/dnserrordiagoff.htm# is correct
Search for this site on Bing
Refresh the page

I afraid it is Windows 10 October update in action.

Anybody, who knows how to fix this, please! Last thing I want is profile re-build.

[DuncanHornby]

All,

Just want to add to this, very pleased to see a fix for this, but the link above is for a specific build so when I tried it it refused to update the PC. Fortunately the IT lot here pointed me to the correct build version I needed, so if your Windows is build 1709 then you need to be going here:

https://www.catalog.update.microsoft.com/Search.aspx?q=%092019-01%20Cumulative%20Update%20for%20Wind...

Just something to be aware of. Well done Chris Ringo for finding this fix, it's been driving me nuts for months!