Code:
[root@kindle root]# cat /mnt/us/developer/Test/work/crash.log
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[05.09.12 11:42] Test (v. 1.0)
java.lang.NoClassDefFoundError: com.amazon.kindle.kindlet.ui.KTextArea
at java.lang.Class.getConstructor0(Native Method)
at com.amazon.kindle.kindlet.internal.vb.D(nzc:370)
at com.amazon.kindle.kindlet.internal.vb.B(nzc:1684)
at com.amazon.kindle.kindlet.internal.lifecycle.l.call(cfd:738)
at edu.emory.mathcs.backport.java.util.concurrent.FutureTask.run(FutureTask.java:178)
at edu.emory.mathcs.backport.java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1029)
at edu.emory.mathcs.backport.java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:547)
at java.lang.Thread.run(Unknown Source)
at java.lang.Thread.startup(Unknown Source)
Ah... I vaguely remember that the K3 used these Amazon-specific classes, while the K5 just uses plain Java Swing. So maybe the kindlet version actually isn't 2.x, but 1.x? Which kindlet-x.y.jar are you using? (it's kindlet-2.1.jar on the K5, obviously).
So yeah, it won't run on the K5 as is, but it actually should on yours. If it's really version 1.x, then it's probably counterproductive to put in all the Specification-Version stuff in the manifest. But then I'm out of the game, as are all other users of newer Kindles.
One last idea: give it a try with a JTextArea instead of a KTextArea. This will work on my device, but I'm not sure about yours