I've been seeing this failure recently. Just observed in 1.328. I'm running on
Mac OS X 10.5.8. Here's the relevant failure output:

Test set: hudson.model.DirectoryBrowserSupportTest
-------------------------------------------------------------------------------
Tests run: 3, Failures: 0, Errors: 1, Skipped: 0, Time elapsed: 4.051 sec <<<
FAILURE!
testNonAsciiChar(hudson.model.DirectoryBrowserSupportTest) Time elapsed: 1.347
sec <<< ERROR!
com.gargoylesoftware.htmlunit.FailingHttpStatusCodeException: 404 Not Found for
http://localhost:63463//job/test0/ws/%e6%bc%a2%e5%ad%97.bin
at
com.gargoylesoftware.htmlunit.WebClient.throwFailingHttpStatusCodeExceptionIfNecessary(WebClient.java:545)
at com.gargoylesoftware.htmlunit.WebClient.getPage(WebClient.java:341)
at com.gargoylesoftware.htmlunit.WebClient.getPage(WebClient.java:390)
at com.gargoylesoftware.htmlunit.WebClient.getPage(WebClient.java:377)
at org.jvnet.hudson.test.HudsonTestCase$WebClient.goTo(HudsonTestCase.java:1149)
at
hudson.model.DirectoryBrowserSupportTest.testNonAsciiChar(DirectoryBrowserSupportTest.java:86)

2009-10-12 18:17:06.195::INFO: jetty-6.1.11
2009-10-12 18:17:06.200::INFO: NO JSP Support for /, did not find
org.apache.jasper.servlet.JspServlet
2009-10-12 18:17:06.204::INFO: Started SocketConnector@0.0.0.0:63457
Oct 12, 2009 6:17:06 PM hudson.ClassicPluginStrategy createPluginWrapper
INFO: Loading plugin:
/var/folders/m/+mVCn5sfERif6nwSiVvoo++m9U/Tmp/hudson6852007366284250730test/plugins/maven-plugin.hpi
Oct 12, 2009 6:17:06 PM hudson.ClassicPluginStrategy explode
INFO: Extracting
/var/folders/m/+mVCn5sfERif6nwSiVvoo++m9U/Tmp/hudson6852007366284250730test/plugins/maven-plugin.hpi
Oct 12, 2009 6:17:07 PM hudson.model.Hudson load
INFO: Loading in 4 parallel threads
Oct 12, 2009 6:17:07 PM hudson.model.Hudson load
INFO: Took 69 ms to load
Oct 12, 2009 6:17:07 PM hudson.TcpSlaveAgentListener <init>
INFO: JNLP slave agent listener started on TCP port 63458
=== Starting DirectoryBrowserSupportTest.testDoubleDots
Oct 12, 2009 6:17:07 PM hudson.model.Run run
INFO: test0 #1 main build action completed: SUCCESS
Oct 12, 2009 6:17:07 PM hudson.PluginWrapper stop
INFO: Stopping maven-plugin
2009-10-12 18:17:08.595::INFO: jetty-6.1.11
2009-10-12 18:17:08.600::INFO: NO JSP Support for /, did not find
org.apache.jasper.servlet.JspServlet
2009-10-12 18:17:08.603::INFO: Started SocketConnector@0.0.0.0:63460
Oct 12, 2009 6:17:08 PM hudson.ClassicPluginStrategy createPluginWrapper
INFO: Loading plugin:
/var/folders/m/+mVCn5sfERif6nwSiVvoo++m9U/Tmp/hudson1365147185419451640test/plugins/maven-plugin.hpi
Oct 12, 2009 6:17:08 PM hudson.ClassicPluginStrategy explode
INFO: Extracting
/var/folders/m/+mVCn5sfERif6nwSiVvoo++m9U/Tmp/hudson1365147185419451640test/plugins/maven-plugin.hpi
Oct 12, 2009 6:17:08 PM hudson.model.Hudson load
INFO: Loading in 4 parallel threads
Oct 12, 2009 6:17:08 PM hudson.model.Hudson load
INFO: Took 77 ms to load
Oct 12, 2009 6:17:08 PM hudson.TcpSlaveAgentListener <init>
INFO: JNLP slave agent listener started on TCP port 63461
=== Starting DirectoryBrowserSupportTest.testDoubleDots2
Oct 12, 2009 6:17:08 PM hudson.model.Run run
INFO: test0 #1 main build action completed: SUCCESS
Oct 12, 2009 6:17:08 PM hudson.PluginWrapper stop
INFO: Stopping maven-plugin
2009-10-12 18:17:09.894::INFO: jetty-6.1.11
2009-10-12 18:17:09.899::INFO: NO JSP Support for /, did not find
org.apache.jasper.servlet.JspServlet
2009-10-12 18:17:09.902::INFO: Started SocketConnector@0.0.0.0:63463
Oct 12, 2009 6:17:09 PM hudson.ClassicPluginStrategy createPluginWrapper
INFO: Loading plugin:
/var/folders/m/+mVCn5sfERif6nwSiVvoo++m9U/Tmp/hudson5425220157078630591test/plugins/maven-plugin.hpi
Oct 12, 2009 6:17:09 PM hudson.ClassicPluginStrategy explode
INFO: Extracting
/var/folders/m/+mVCn5sfERif6nwSiVvoo++m9U/Tmp/hudson5425220157078630591test/plugins/maven-plugin.hpi
Oct 12, 2009 6:17:09 PM hudson.model.Hudson load
INFO: Loading in 4 parallel threads
Oct 12, 2009 6:17:09 PM hudson.model.Hudson load
INFO: Took 77 ms to load
Oct 12, 2009 6:17:09 PM hudson.TcpSlaveAgentListener <init>
INFO: JNLP slave agent listener started on TCP port 63464
=== Starting DirectoryBrowserSupportTest.testNonAsciiChar
Oct 12, 2009 6:17:10 PM hudson.model.Run run
INFO: test0 #1 main build action completed: SUCCESS
Oct 12, 2009 6:17:10 PM com.gargoylesoftware.htmlunit.WebClient
printContentIfNecessary
INFO: statusCode=[404] contentType=[text/html]
Oct 12, 2009 6:17:10 PM com.gargoylesoftware.htmlunit.WebClient
printContentIfNecessary
INFO: <html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"/>
<title>Error 404 NOT_FOUND</title>
</head>
<body><h2>HTTP ERROR: 404</h2><pre>NOT_FOUND</pre>
<p>RequestURI=//job/test0/ws/%e6%bc%a2%e5%ad%97.bin</p><p><i><small><a
href="http://jetty.mortbay.org/">Powered by Jetty://</a></small></i></p><br/>

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</body>
</html>

Oct 12, 2009 6:17:10 PM hudson.PluginWrapper stop
INFO: Stopping maven-plugin