Thinkpad S440 running Windows 10
Using the Haswell-generation Intel integrated GPU that came with the i5.
Additionally have an AMD 8670M, but not using it with Blender.
Short description of error
The UI only updates when you resize the window, not when input (clicking, keypresses) is received unless you disable High Contrast mode.
Exact steps for others to reproduce the error
Make sure you save your Windows 10 theme first so you don't lose it.
Search for "high contrast" in Windows 10.
Select "High Contrast #1" from the theme picker and click apply.
The window remains grey.
The contents are now shown.
Try clicking in the viewport around the splash screen.
Resize the window.
The splash screen is now gone; it had accepted your input, but not updated the display.
Similar input like clicking on the menu bar or dragging in the viewport exhibits the same symptoms.
The only workaround is to disable high contrast mode.