Tried so far:
Process: Uninstall CRD from CP. Reboot now to ensure service is removed.
Install new .msi 
Once installed, the service is not running and throws a 1053 error if you try and start it from services.msc. Back to square one.

Tried via admin dos prompt:
C:\WINDOWS>net start chromoting
The service is not responding to the control function.
More help is available by typing NET HELPMSG 2186.

C:\WINDOWS>net helpmsg 2186
The service is not responding to the control function.
EXPLANATION
The service cannot run your command at this time.

Also ran sawbuck,  chromoting set to show all, verbose, trying to start the service with either services.msc or net start...  creates no errors in sawbuck.

If I open the remote desktop app, I get as per file attached...

Deleted: sawbuck1.log 2.6 KB

sawbuck1.log 2.6 KB View Download

Ok, on a couple of machines I've managed to get it working again, I found a previous version online and persuaded it to install... Though now I need to find out how to stop it re-updating itself until it's hopefully fixed...
 

Unable to reproduce the issue on Win 7,Mac 10.11.3 and Ubuntu 14.04 using CRD version # 50.0.2661.22 and chrome version 49.0.2623.110,51.0.2693.2 and 51.0.2698.0.
Was able to access Mac and Ubuntu from Windows without any issues.
joedow@ : Assigned to you based on the comment # 15 on issue 599122.

Had to block all google updates to keep it working. Interestingly there's quite a lot of variation between machines as to what's there for updates! Between 0 and 3 services, and 2 - 4 scheduled tasks! This helped / confirmed same:  http://goo.gl/EthAZr

Problem occurs for me on Win 7 64 bit and win XP SP3.

Reversion to 49.0.2623.40\remoting_host.exe fixes it, with update problem as above.

App version is 50.0.2661.22 by the way.

Thanks, just to confirm for gpa@'s issue, the failing host version was 51.0.2693.2?  Which SKU of Windows 7 was this (home/enterprise/etc).

Did you try a host in the 50.n.nnnn.n range?

Lastly, App version shouldn't play into problems starting the host service.

Thanks,
Joe

As of today, I get 50.0.2661.22 if it updates (reading from services.msc).
51.0.2693.2 hasn't rolled out to any machines here yet!
Win 7 vers are "ultimate" (there's a misnomer...)
XP vers are SP3.

The WinXP issue is different ( crbug.com/600144 ).

For Win7, would you mind grabbing a log file from process monitor?
https://technet.microsoft.com/en-us/sysinternals/processmonitor.aspx

With ProcMon.exe running, press CTRL+L to open the filter dialog.  Add a filter for 'Remoting_Host.exe' as the process name, then attempt to start the service.  Then save and attach the log file.  Hopefully that will give me an idea of what is failing.

Win XP -- is there a fix in the pipeline then?
I'll get a W7 log as soon as I can get to a machine!

Any luck retrieving the Procmon log for Win7?

Not as yet, sorry. I got to the machine that worked with the "xp fix", that had failed before. I removed that by reinstalling CRD... And, murphy's law, it still worked.. Hmm...

OK, I'm going to resolve the bug for now, but please reactive if you see this problem again and can gather the additional log info.

No problem... Typical though, things never break when you need them too!