Testcase org.jboss.as.test.integration.ejb.timerservice.mgmt.NonPersistentIntervalTimerManagementTestCase fails sometimes for me when running build with all tests on Windows machine. I never saw this failure on my Solaris box using the same JDK version. And somehow the appearance of the failure seem to be related to the execution time.
Executing the testsuite during the day does not show me this error. Only in the very late evening / early morning hours the error appeared. (All related to Central European Summer time in my case.)

I added some debug output an saw, that, in case of failure, after "activateTimer" the timer fires immediately so that there is one timeout too much then. The initial timeout time of the timer is passed, when it's suspended. When activated it seems to make good for the missed timeout sometimes.
The persistent version of this testcase located in the same package with exactly same logic never fails for me.