Latronix KVM stopped working after last java update
Once I reverted back to the Apple provided java packages, it fixed my problems.

The article for this download is:


Java for OS X 2012-006: How to re-enable the Apple-provided Java SE 6 applet plug-in and Web Start functionality


Update: Note that for some people, the Java 7 update works with Lantronix Spiders. I can confirm that a colleague with the same model Macbook Pro has no problems using the latest Java 7 update. Another with a Macbook Air experiences the same issue, which is also resolved by rolling back.