There appears to be an issue with the TestLink plugin when the TAP plugin is also installed and a job config is using both. Here's the first few lines of the exception we're seeing in jenkins.log:

WARNING: Skipping a non-existent field comments
com.thoughtworks.xstream.converters.reflection.MissingFieldException: No field 'comments' found in class 'org.tap4j.model.TestResult'
at com.thoughtworks.xstream.converters.reflection.FieldDictionary.field(FieldDictionary.java:94)

Attached are 3 files that you can use to help illustrate and debug this issue:

jenkins_config.xml – A minimal jenkins system config.xml
job_config.xml – A minimal job config.xml
jenkins.log – Jenkins system log with the full exceptions after a fresh jenkins start

This issue may be related to the following issues:

https://issues.jenkins-ci.org/browse/JENKINS-17488
https://issues.jenkins-ci.org/browse/JENKINS-17215