I guess your opponent is running Vassal on Windows, but please specify.
Vassal for Windows runs its own embedded Java Virtual Machine (JVM), so it doesn’t matter if your opponents general JVM is up-to-date or not. However, your assertion seems to indicate a more general problem with JVMs on your opponents machine.
From your screenshot, it looks like you opponent is running Vassal on Windows and it is version 3.7.17 of Vassal and 2.3 of the module in question. But I cannot find version 2.3 of Starship Troopers in the module library - only
- Starship Troopers
Starship_Trooperswith versions 2.11.0, 2.1.0, 1.2.0, and 1.1.0 - Starship Troopers
Starship_Troopers_enhancedwith versions 3.2.1, 3.1.1, and 3.0.0-final - Starship Troopers
Starship_Troopers_lonestarwith versions 1.3.4, 1.3.3, 1.3.2, 1.3.1, 1.1.0, 1.0.1, and 1.0.0
Please specify which module (preferably with a link) your opponent is using.
See also How to report problems.
See also “Tearing” on maps and other Graphics Issues
Yours,
Christian