I have been running jEdit 5.3 for about 1.5 years with no significant problem. On 2017-07-03 I used it and it worked fine. On 2017-07-04, it would not start. jedit and javaw exe's were created, but the jEdit window did not display. I uninstalled version 5.3 and tried to install version 5.4 and got this error: "The installer will now try to quit a running instance of jEdit. Please save your work and exit jEdit for the installation to continue." When I continue, the installer freezes. The same happens if I try to install version 5.3. I did not have a running instance, but the installer thought that I had one. I am guessing that something went wrong with jEdit when I shutdown on the 3rd. (I always intend to close all apps before I shut down, it is possible that I forgot to shutdown jEdit.) Does anyone know how to tell windows 7 to get rid of this phantom instance of jEdit. I am using a backup version of jEdit 4.5.2 for the time being. So, I can continue with my work. I am guessing that this phantom instance also caused the jEdit 5.3 startup problem that I had before the uninstall. 2017-07-15 Update: I tried installing jEdit 5.4 on Saturday and it worked! On my previous try, when I got the 'running instance' warning I stopped, because every other time I continued at the point the installation froze. On Saturday, I tried continuing after the warning, and it worked! My thanks to Ross Rogers and Mr. Vampire for taking the time to give me expert advice. Renaming the roaming jedit file apparently was effective. I am guessing that deleting the server file would have helped also.
The most likely cause is a stale server file that points to some other process. jEdit and the installer talks to running instances via the network (TCP) on a port that is opened randomly and written to the server file in your settings directory. If you do not quit jEdit cleanly (e. g. only close the window without using the file menu or the shortcut to completely quit jEdit when the jEdit server is running), then jEdit on next start (or the installer) finds the server file and tried to talk to the process listening on the port written in the file. If there is no process listening, it is assumed that the server file is stale and a new instance of jEdit is started. Unfortunately jEdit is not as grateful if there is some process listening on that port but is not answering, jEdit just waits forever currently. This definitely needs to be improved and I think there is also a ticket for this. Try to delete the server file in your settings directory, by default it is %APPDATA%/jEdit/server on Windows and then try to start jEdit or the installer again.