There have not been any changes, but this test uses the unreliable Thread.stop call. The call is ending with a ThreadDeath that is not being handled. Its not clear why this test would have worked in the past as BasicThreadPool.run never has handled this exception. I guess some vms are not throwing it.

18:31:59,256 WARN [RunnableTaskWrapper] Unhandled throwable for runnable: org.jboss.test.util.test.ThreadPoolRunnableUnitTestCase$TestRunnable@be41ec
java.lang.ThreadDeath
 at java.lang.Thread.stop(Thread.java:698)
 at org.jboss.util.threadpool.RunnableTaskWrapper.stopTask(RunnableTaskWrapper.java:122)
 at org.jboss.util.threadpool.BasicThreadPool$TimeoutInfo.stopTask(BasicThreadPool.java:517)
 at org.jboss.util.threadpool.BasicThreadPool$TimeoutMonitor.run(BasicThreadPool.java:579)
 at java.lang.Thread.run(Thread.java:595)

The source is clearly different, with the brew version clearly missing two changes. This is a source tree older than 1.3.4 to be sure:

[starksm@succubus oswego-concurrent]$ diff -w 1.3.4/lib/src/EDU/oswego/cs/dl/util/concurrent/PooledExecutor.java 1.3.4-brew/src/concurrent/PooledExecutor.java
30,31d29
< 30aug2003 dl check for new tasks when timing out
< 18feb2004 dl replace dead thread if no others left
190,193c188
< * <dd> Wait until a thread becomes available. This
< * policy should, in general, not be used if the minimum number of
< * of threads is zero, in which case a thread may never become
< * available.
---
> * <dd> Wait until a thread becomes available.
298c293
< * <li> Same as (2) except clients abort if both the buffer is full and
---
> * <li> Same as (2) except clients block if both the buffer is full and
304c299
< * pool.abortWhenBlocked();
---
> * pool.waitWhenBlocked();
699,709d693
<
< // Create a replacement if needed
< if (poolSize_ == 0 || poolSize_ < minimumPoolSize_) {
< try {
< Runnable r = (Runnable)(handOff_.poll(0));
< if (r != null && !shutdown_) // just consume task if shut down
< addThread(r);
< } catch(InterruptedException ie) {
< return;
< }
< }
794,797d777
< synchronized(PooledExecutor.this) {
< if (shutdown_)
< return true;
< }
805,806c785
< * is available, unless the pool has been shut down, in which case
< * the action is discarded.
---
> * is available.

You are supposed to be using http://repository.jboss.org/oswego-concurrent/1.3.4.patch01-brew/
which has the patches:
concurrent-ConcurrentHashMap.patch
concurrent-ConcurrentReaderHashMap.patch
concurrent-PooledExecutor.patch

I have no idea how the unpatched 1.3.4-brew ended up in Branch_4_2.

P.S.: I myself run the testsuite after any component upgrade, -brew or not.