Using Jenkins 1.526 and ivyTrigger 0.30 polling always fails.
Checking the logs I see nothing.

Interestingly when enabling debug on the ivyTrigger for that job and disabling it afterwards (while allowing the job to build in-between) seems to solve the issue only on that particular job. When Jenkins is restarted the problem is back.

Exact output:

[IvyTrigger] - Poll with an Ivy script

Polling started on Sep 3, 2013 6:33:48 PM
Polling for the job XXXXXXXX
Looking nodes where the poll can be run.
Looking for the last built on node.

Polling on master.
[ERROR] - Polling error...