I downloaded ZK 3.4.3 sources and ran ant test. Many of the tests failed, including ZooKeeperTest. A common symptom was spurious ConnectionLossException:
2012-06-01 12:01:23,420 [myid:] - INFO [main:JUnit4ZKTestRunner$LoggedInvokeMethod@54] - TEST METHOD FAILED testDeleteRecursiveAsync
org.apache.zookeeper.KeeperException$ConnectionLossException: KeeperErrorCode = ConnectionLoss for /
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
As background, I was actually investigating some non-deterministic failures when using Netflix's Curator with Java 7 (see https://github.com/Netflix/curator/issues/79). After a while, I figured I should establish a clean ZK baseline first and realized it is actually a ZK issue, not a Curator issue.
We are trying to migrate to Java 7 but this is a blocking issue for us right now.