I can no longer view the serial monitor, the window seems to exist but when I click on it from the taskbar nothing happens. I have installed the latest version of Java and reinstalled the Arduino IDE.
There was a similar problem here but no solution was posted:
JAVA_HOME is in my program files...
1. Locate the preferences.txt file (the path is shown in the "Preferences" window)
2. Exit the IDE,
3. search for "last.serial"
4. set it to something like: last.serial.location=0,0,500,500
5. restart the IDE
Make sure those numbers are something reasonable. That should put it in the upper left corner if I remember correctly.
Thanks so much, this was driving me crazy!