Difficulties launching MinimWatch with MinimServer on Windows 8.1

[DavidHB]

I have had MinimServer and MinimWatch running together normally on my Windows 7 machine for some time now, but only today decided to install them on my Windows 8.1 machine.

MinimServer starts normally on its own, with the following log:

MinimServer 0.8.3 update 55, Copyright © 2012-2014 Simon Nash. All rights reserved.
Java™ SE Runtime Environment (build 1.8.0_25-b18)
Java HotSpot™ 64-Bit Server VM (build 25.25-b02, mixed mode)
Platform default charset is windows-1252
Language setting is 'eng'
starting MinimServer[XYZ]
MinimServer[XYZ] is running
Startup complete

If I then attempt to start MinimWatch, it fails (no instances of MinimServer elsewhere on the network are reported, and the tray icon has a red minim) with the following log:

MinimWatch 0.8.3 update 30, Copyright © 2012-2014 Simon Nash. All rights reserved.
Java™ SE Runtime Environment (build 1.8.0_25-b18)
Java HotSpot™ 64-Bit Server VM (build 25.25-b02, mixed mode)
Platform default charset is windows-1252
Unable to delete old module file C:\Users\Owner\AppData\Roaming\MinimServer\libext\jminim-0.6.201.jar
Startup complete

If I then close MinimServer, and try to start MinimWatch on its own, it still fails, but with a different error message:

MinimWatch 0.8.3 update 30, Copyright © 2012-2014 Simon Nash. All rights reserved.
MinimStreamer 0.5, Copyright © 2012-2014 Simon Nash. All rights reserved.
Java™ SE Runtime Environment (build 1.8.0_25-b18)
Java HotSpot™ 64-Bit Server VM (build 25.25-b02, mixed mode)
Platform default charset is windows-1252
Previously installed package minimstreamer-0.5 conflicts with this installation
Startup complete

For comparison, the corresponding MinimWatch log on my Windows 7 machine (reporting on instances of MinimServer on the NAS and the Windows 8.1 machine) is as follows:

MinimWatch 0.8.3 update 30, Copyright © 2012-2014 Simon Nash. All rights reserved.
Java™ SE Runtime Environment (build 1.7.0_25-b17)
Java HotSpot™ 64-Bit Server VM (build 23.25-b01, mixed mode)
Platform default charset is windows-1252
Active subnet is 192.168.0.0
Startup complete
MinimServer[XYZ] is running
MinimServer[ABC-NAS] is running

(Note that the to me surprising reference to MinimStreamer does not appear in this log.)

If I then try to start MinimServer with the MinimWatch tray icon still showing, I get the red mimim tray icon and the following log:

MinimServer 0.8.3 update 50, Copyright © 2012-2014 Simon Nash. All rights reserved.
Java™ SE Runtime Environment (build 1.8.0_25-b18)
Java HotSpot™ 64-Bit Server VM (build 25.25-b02, mixed mode)
Platform default charset is windows-1252
Unable to delete old module file C:\Users\Owner\AppData\Roaming\MinimServer\libext\jminim-0.6.201.jar
Startup complete

It appears that whichever of MinimServer and MinimWatch is started second fails with the "Unable to delete ..." message.

I'd be grateful for advice on these findings.

David