Windows 10 Home up to date.  ASUS PB287Q 4K 28" monitor.  EVGA GTX980 video card w/355.82 driver installed.  Monitor connected to video card via Display Port 2.  ASUS Z97 Deluxe USB 3.1 motherboard with current UEFI flashed and 16GB Crucial memory. 
 
For years I've kept the task bar located at the bottom of the screen with auto hide activated but now there is a problem.  When the computer wakes from sleep mode the task bar will not show or work until I CAD to open the task manager and then restart Windows Explorer.  The task bar will then function normally until the computer enters sleep mode again and the issue will return forcing a restart of Windows Explorer.  I discovered that if I put the task bar on the left side of the screen it will not be effected by sleep mode and will function normally after sleep mode.  Problem is after years of having the task bar at the bottom of the screen it is awkward having it on the left.
 
I hooked up a different monitor with a DVI connector and it functioned normally with no task bar issue.  Hooked the ASUS monitor back up and the task bar issue returned.  Removed the Display Port connection and hooked up an HDMI cable and voila! the task bar functioned normally at the bottom of the screen and no issue with sleep mode.  Returned to the Display Port connection and the task bar issue is back.  ASUS tech support suggested resetting the monitor to factory defaults which I did.  Another suggestion was removing the NVIDIA driver and reinstalling which I also did but neither action corrected the task bar issue.  I'm quite happy with the ASUS monitor and the graphics are awesome so I would like to retain the Display Port connection as recommended for a 4K monitor setup.
 
At this point in time I'm not sure if it is a video card issue possibly with the display port connection or a monitor issue with its display port connection.  Windows 10 is a possibility I suppose since I have to restart Windows Explorer to get a working task bar.  I've reached the limit of my troubleshooting knowledge and I don't know if there is anything left to do that will let me know where the problem lies.  I don't know anyone with a computer with a display port capability so I can't hook the monitor to another machine. 
 
 

I have a couple of blank SSDs so  I might see if I can get a different version of Windows installed. 
 
 
 
 

I reckon I've narrowed it down to some kind of conflict with Windows 10 and my hardware or just a Windows 10 hiccup.  I installed a copy of Windows 8.1 this morning and everything worked and no task bar issue.  I do have a 2nd computer with Windows 10 installed and it does not have the task bar problem, but it has different hardware.  I guess I'll post this up on Windows Insider to see what transpires.