Arduino ide not loading

I just updated an old copy of the Arduino IDE to the latest version, and when I tried to launch, it would get as far as the splash screen and then exit.
After a lot of swearing, I ran the arduino_debug command from a command prompt and it pointed me in the right direction.
I found that the Preferences.txt file in the Users\AppData\Local\Arduino15 folder had installed as read only. I unchecked the its read only status and it’s all sorted, everything is OK now.
Just thought I would pass on the experience just in case it was of some help to others.
Never had an issue before, so it was a bit of a surprise.