Every day or so I get errors like this when starting a slave:

ERROR: The instance ID 'i-6fdc2512' does not exist
Status Code: 400, AWS Service: AmazonEC2, AWS Request ID: 195aae09-8d42-4f24-9a30-2d31b7447818, AWS Error Code: InvalidInstanceID.NotFound, AWS Error Message: The instance ID 'i-6fdc2512' does not exist
at com.amazonaws.http.AmazonHttpClient.handleErrorResponse(AmazonHttpClient.java:547)
at com.amazonaws.http.AmazonHttpClient.executeHelper(AmazonHttpClient.java:284)
at com.amazonaws.http.AmazonHttpClient.execute(AmazonHttpClient.java:169)
at com.amazonaws.services.ec2.AmazonEC2Client.invoke(AmazonEC2Client.java:5684)
at com.amazonaws.services.ec2.AmazonEC2Client.describeInstances(AmazonEC2Client.java:2543)
at hudson.plugins.ec2.EC2Computer._describeInstance(EC2Computer.java:97)
at hudson.plugins.ec2.EC2Computer.getState(EC2Computer.java:76)
at hudson.plugins.ec2.EC2ComputerLauncher.launch(EC2ComputerLauncher.java:33)
at hudson.slaves.SlaveComputer$1.call(SlaveComputer.java:200)
at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:303)
at java.util.concurrent.FutureTask.run(FutureTask.java:138)
at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
at java.lang.Thread.run(Thread.java:662)

and I have to manually delete them to unblock jobs. The odd part is that this instance actually does exists on the EC2 Mgmnt console. Any idea what this is about and how I can resolve it ?

-John