The EC2 plugin fails to launch a slave with this error about half the time. I had this issue originally on Jenkins 1.443 and upgraded to 1.450 and it still occurs.

Let me know what else I can provide for this issue.

ERROR: Client error : The instance ID 'i-331f8856' does not exist
com.xerox.amazonws.ec2.EC2Exception: Client error : The instance ID 'i-331f8856' does not exist
at com.xerox.amazonws.ec2.Jec2.makeRequestInt(Jec2.java:2359)
at com.xerox.amazonws.ec2.Jec2.describeInstances(Jec2.java:826)
at hudson.plugins.ec2.EC2Computer._describeInstance(EC2Computer.java:94)
at hudson.plugins.ec2.EC2Computer.getState(EC2Computer.java:75)
at hudson.plugins.ec2.EC2ComputerLauncher.launch(EC2ComputerLauncher.java:29)
at hudson.slaves.SlaveComputer$1.call(SlaveComputer.java:200)
at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:334)
at java.util.concurrent.FutureTask.run(FutureTask.java:166)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603)
at java.lang.Thread.run(Thread.java:636)