4.1.3.1708 Focus jumps out of tree pane

[WahWahWeeks]

I'm using MM4 4.1.3.1708 on Windows 7, Dell i5 laptop with 8GB RAM.
After 50% of starts, I click on a folder and the focus immediately jumps unbidden from the navigation tree pane into the track list pane.
So that I have to use the mouse on the triangle to open a folder instead of using left and down arrow keys.
Thanks for the great digital music system.