When Panning the map using right mouse button

[Ben97]

What steps will reproduce the problem?

1. Use the right mouse button to pan the map

What is the expected result?

The map moves, nothing else

What happens instead?

The map moves, but when releasing the button a dropdown menu opens. The dropdown menu is the same as when not moving the mouse and simply click the right mouse button.

Please provide any additional information below. Attach a screenshot if possible.

This problem happens only on one of my computers. The computer with problens is the one with the following data.
I tried to reinstall JOSM, but that didn't change anything

URL:http://josm.openstreetmap.de/svn/trunk
Repository:UUID: 0c6e7542-c601-0410-84e7-c038aed88b3b
Last:Changed Date: 2017-05-29 16:19:58 +0200 (Mon, 29 May 2017)
Build-Date:2017-05-29 14:25:03
Revision:12275
Relative:URL: ^/trunk

Identification: JOSM/1.5 (12275 de) Windows 7 64-Bit
OS Build number: Windows 7 Home Premium null (7601)
Memory Usage: 703 MB / 1801 MB (182 MB allocated, but free)
Java version: 1.8.0_131-b11, Oracle Corporation, Java HotSpot(TM) 64-Bit Server VM
Screen: \Display0 1366x768
Maximum Screen Size: 1366x768
VM arguments: [-Djava.security.manager, -Djava.security.policy=file:<java.home>\lib\security\javaws.policy, -DtrustProxy=true, -Djnlpx.home=<java.home>\bin, -Djnlpx.origFilenameArg=%UserProfile%\AppData\LocalLow\Sun\Java\Deployment\cache\6.0\56\1ee8cfb8-2857e846, -Djnlpx.remove=false, -Djava.util.Arrays.useLegacyMergeSort=true, -Djnlpx.splashport=49202, -Djnlp.application.href=https://josm.openstreetmap.de/download/josm.jnlp, -Djnlpx.jvm=<java.home>\bin\javaw.exe]
Dataset consistency test: No problems found

Plugins:
+ FixAddresses (33182)
+ buildings_tools (33004)
+ log4j (32699)

Last errors/warnings:
- W: java.io.IOException: Attribution is not loaded yet
- W: java.io.IOException: Attribution is not loaded yet
- W: java.io.IOException: Attribution is not loaded yet
- W: java.io.IOException: Attribution is not loaded yet
- W: java.net.SocketTimeoutException: Read timed out
- W: java.net.SocketTimeoutException: Read timed out
- W: java.net.SocketTimeoutException: Read timed out
- W: java.net.SocketTimeoutException: Read timed out
- W: java.net.SocketTimeoutException: Read timed out
- W: java.net.SocketTimeoutException: Read timed out

[Don-vip]

Is your PC a desktop or laptop? If laptop, which model please? Have you tried to update your mouse/touchpad drivers? It does not sound like a JOSM bug.