Some more evidence that hopefully will help.
Just turned laptop on and the mouse click only worked to drag a box on the desktop. But couldnt use it to active the taskbar at the bottom ((usually, dragging over with the mouse will make the task bar pop up).
I also couldnt click on anything on the taskbar or start bar.
But I could drag and make boxes on the desktop holding left click down.
CTRL ALT DEL brings the mouse back and I can once again use the mouse as it should be used.
Sometimes this will last for a while.. sometimes the whole session. Other times, I will keep needing to repeat the CTRL ALT DEL to get it back lots of times.
As I say, it is not a hardware issue. Wonder what it is?