Starting in version 0.10, Hudson can't find usable Java on our OSX and Linux slaves. Issue seems to be caused by the patch for issue #6005, which started using NumberFormat for parsing Java version. We happen to be using a locale (fi) that uses comma instead of dot for decimal sperator and thus parsing something like "1.6.0_17" given by "java -version" yields just 1.0, causing version check to fail.

Log from trying to start OSX slave:
[05/05/10 03:20:36] [SSH] Checking java version of java
[05/05/10 03:20:37] [SSH] java -version returned 1.6.0_17.
[05/05/10 03:20:37] [SSH] Checking java version of /usr/bin/java
[05/05/10 03:20:37] [SSH] /usr/bin/java -version returned 1.6.0_17.
[05/05/10 03:20:37] [SSH] Checking java version of /usr/java/default/bin/java
Couldn't figure out the Java version of /usr/java/default/bin/java
bash: /usr/java/default/bin/java: No such file or directory

[05/05/10 03:20:37] [SSH] Checking java version of /usr/java/latest/bin/java
Couldn't figure out the Java version of /usr/java/latest/bin/java
bash: /usr/java/latest/bin/java: No such file or directory

[05/05/10 03:20:37] [SSH] Checking java version of /usr/local/bin/java
Couldn't figure out the Java version of /usr/local/bin/java
bash: /usr/local/bin/java: No such file or directory

[05/05/10 03:20:37] [SSH] Checking java version of /usr/local/java/bin/java
Couldn't figure out the Java version of /usr/local/java/bin/java
bash: /usr/local/java/bin/java: No such file or directory

[05/05/10 03:20:37] [SSH] Checking java version of /hudson/jdk/bin/java
Couldn't figure out the Java version of /hudson/jdk/bin/java
bash: /hudson/jdk/bin/java: No such file or directory

Darwin name.domain.com 10.3.0 Darwin Kernel Version 10.3.0: Fri Feb 26 11:58:09 PST 2010; root:xnu-1504.3.12~1/RELEASE_I386 i386
hudson.util.IOException2: Could not find any known supported java version in [java, /usr/bin/java, /usr/java/default/bin/java, /usr/java/latest/bin/java, /usr/local/bin/java, /usr/local/java/bin/java, /hudson/jdk/bin/java], and we also failed to install JDK as a fallback
at hudson.plugins.sshslaves.SSHLauncher.launch(SSHLauncher.java:200)
at hudson.slaves.SlaveComputer$1.call(SlaveComputer.java:183)
at java.util.concurrent.FutureTask$Sync.innerRun(Unknown Source)
at java.util.concurrent.FutureTask.run(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)
Caused by: java.io.IOException: Failed to detect the environment for automatic JDK installation. Please report this to users@hudson.dev.java.net: Darwin name.domain.com 10.3.0 Darwin Kernel Version 10.3.0: Fri Feb 26 11:58:09 PST 2010; root:xnu-1504.3.12~1/RELEASE_I386 i386

at hudson.plugins.sshslaves.SSHLauncher.attemptToInstallJDK(SSHLauncher.java:268)
at hudson.plugins.sshslaves.SSHLauncher.launch(SSHLauncher.java:198)
... 6 more
[05/05/10 03:20:37] [SSH] Connection closed.