Thanks for the early advice.
The PC link version is the latest 5.6.7.3632.
I'm using EN-JP set up package in Japanese environment.
In addition, the connection with ECU is USB3, but even if it does not connect to ECU, the start of the program is slow, the PClink window does not stand up for about one minute after the icon click, and the click reaction of the menu bar is made to wait for about one minute more.
It may be a problem specific to the Japanese environment (or 2-byte characters), because it occurs in Japan in many cases besides me.
I also searched the previous thread in the advice, Slow reacting By Highlift, May 1, 2017 in G4+, which I think is it!
If the issue with the graphics driver and USB3 has been fixed in the update, it may be a problem with the Japanese environment.