The JNA library will, by default, first check the system for jnidispatch.dll rather than extract it from the jar.

There's an issue when Arduino starts in 32-bit mode and then suddenly tries to load 64-bit jnidispatch.dll from the system path. Also, there is the issue of a conflicting version of jnidispatch.dll being present and mistakenly used.

Symptoms on Arduino 1.0.5r2 are seeing the splash screen, and then nothing. Arduino 1.5.6r2 shows the splash screen for longer, and then shows a "Launch4j: An error occurred while starting the application" message. If you work out how to display debug messages, you will get "java.lang.UnsatisfiedLinkError" and "com.sun.jna.Native.pointerSize()I"

This issue is comes from Processing, and has been reported here: processing/processing#2239

Resolution is simple - set the jna.nosys Java property to true i.e. -Djna.nosys=true