Setup was unable to close all applications that need to be updated.
?
It would be really helpful if your post consisted of more than just a quoted message and maybe contain an actual question, a description of what you did and what you expected.
I was installing the new update, when the updater says "setup was unable to automatically close all applications."
And does not want to continue.
Right at the start. I have never seen this before and do not have any applications open that would cause this.
Know what this is?
That means that OpenMPT was still running - it could mean that either the instance that started the update was very slow to shut down for an unknown reason, or that you had a second instance running in parallel. An application cannot be updated while it's running on Windows, so all instances of OpenMPT must be closed in order to proceed.
Yeah, that seems to have been the problem. (slow in closing the window or didnt.)
Usually the application should close pretty much instantly, so that's strange. Maybe with future updates you can check if you notice a pattern, i.e. does it always happen, or maybe only if a lot of songs were open, or if audio was playing when triggering the update, etc...