Slow ‘Tools’ menu in Arduino IDE

On a windows machine, the  Arduino IDE can sometimes be rather slow in opening and  can take up to 30 seconds before the ‘Tools’ Menu will open. Supposedly this is due to the fact that a port-scan is made, where especially if bluetooth dongles are used, Windows may wait long for a time out.
The problem and a solution are described here. (Road to solve the delay on the Arduino IDE.)
The solution is to replace the rxtxSerial.dll.