I'm having the same problem on a Windows 10, 64bit, Intel Xeon E3, lots of memory, Clipboard Help+Spell is up to date.  When I start CH+S I see a flash on the screen and the icon shows for half a second in the tray and then vanishes.  After, I see it in the Task Manager running as 32bit. I tried <CTRL><ALT><M> as flowergardener suggested and my KatMouse icon reappeared, but not CH+S. 

Is <CTRL><ALT><M> meant to bring back all missing icons in the tray or is that a specific key for CH+S?  I don't use hotkeys at all and usually disable them when I remember. 

I looked in KatMouse for the hotkey settings to disable, and potentially solve a conflict, but there are no hotkey settings.  I have already tried a restart, but went to try "Restart Explorer by Lee Whittington - it's part of Ultimate Windows Customizer" suggested by IainB but it says it won't run on Windows 10 Pro after I install.

SOLVED!!!: I opened up CH+S on my laptop, saw the hotkey for Show/Hide CHS Window is <CTRL><ALT><W>.  CH+S popped right up.  Hope this helps someone.

Thanks Stoic Joker.  You put out a few facts I didn't understand.  I did know that it "...only controls my personal domain with a small number of mailboxes..." 

You wrote that "...a full blown Exchange implementation because it would cut too far into what I have available for experimentation. ...,"  but later you wrote that "It really is amazing how few resources a server OS requires when it isn't having to futz with the hardware."  I'm sure you're happy with hMailServer, but I'm wondering hypothetically if Exchange is feasible for you if you ignore the modest (for a few years old setup) cost and curtail or batch erase the logs on a small home setup like this.

That must be one hell of a calendar! cheesy I do believe it is safe to say that Virtualization is by far my favorite technology to play with.

I ended up with the system mostly to have fun with virtualization.  I've become addicted to the Calendar since, even though it's just keeping my doctor's appointments and reminding me when to eat my health foods mostly.  If something goes wrong I'm going to buy a subscription to Exchange email somewhere.  Like you, my setup is strictly for my home network lab, but definitely no MSDN subscriptions connected.  Maybe a deploy or two every few years, or a network tool to try, and my WSUS (Windows Updates).

I don't think there is any MS OS that can't be run on Hyper-V - I've got a copy of DOS v6.22...

Wow!  I always thought those compatibilities lists at Microsoft were the Tablets of Moses, Volume 3, especially after reading forums on different hurdles after a bunch of searches over the years.

... a list of caveats a mile long with self hosting..., ...your ISP allows it...

I doubt I'd consider a mail server without a static IP, which requires a Business package from my provider.  There's at least one way around that with DynDns, but again my novice senses tell me to go with the true static in this case.

I love this little handy program but it's now taking about 4% of my CPU in Windows 8.1 64-bit Pro.  I just wrote a batch that will taskkill it after two minutes, since I just use it to set my startup windows and don't need it after.  I'm just writing to try and inspire an update.  With the deeper configuration possibilities than the other One-Hour's this program gets my vote for high priority.  Thanks again.