Application crashes whele multiple applications accessing url.properties. with the following Error on Vista.

This may be corner case and I have got it around 2 times out of 7 tries. Looks like an issue while accessing same file by multiple process.

Error downloading bundle for javax/swing/JFrame.class:
java.lang.NullPointerException: Unable to determine URL for bundle: Bundle[javax_swing_core]
        at sun.jkernel.Bundle.getURL(Unknown Source)
        at sun.jkernel.Bundle.download(Unknown Source)
        at sun.jkernel.Bundle.install(Unknown Source)
        at sun.jkernel.Bundle.install(Unknown Source)
        at sun.jkernel.DownloadManager.doGetBootClassPathEntryForResource(Unknown Source)
        at sun.jkernel.DownloadManager.access$600(Unknown Source)
        at sun.jkernel.DownloadManager$3.run(Unknown Source)
        at java.security.AccessController.doPrivileged(Native Method)
        at sun.jkernel.DownloadManager.getBootClassPathEntryForResource(UnknownSource)
        at sun.jkernel.DownloadManager.getBootClassPathEntryForClass(Unknown Source)
        at java.lang.ClassLoader.findBootstrapClass(Native Method)
        at java.lang.ClassLoader.findBootstrapClass0(Unknown Source)
        at java.lang.ClassLoader.loadClass(Unknown Source)
        at java.lang.ClassLoader.loadClass(Unknown Source)
        at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
        at java.lang.ClassLoader.loadClass(Unknown Source)
        at java.lang.ClassLoader.loadClassInternal(Unknown Source)
Exception in thread "main" java.lang.NoClassDefFoundError: javax/swing/JFrame
        at java.lang.ClassLoader.findBootstrapClass(Native Method)
        at java.lang.ClassLoader.findBootstrapClass0(Unknown Source)
        at java.lang.ClassLoader.loadClass(Unknown Source)
        at java.lang.ClassLoader.loadClass(Unknown Source)
        at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
        at java.lang.ClassLoader.loadClass(Unknown Source)
        at java.lang.ClassLoader.loadClassInternal(Unknown Source)
DownloadManager.download caught: java.io.FileNotFoundException: C:\Program Files\Java\jre6\lib\bundles\urls.properties (The process cannot access the file because it is being used by another process)
java.io.FileNotFoundException: C:\Program Files\Java\jre6\lib\bundles\urls.properties (The process cannot access the file because it is being used by another process)
        at java.io.FileInputStream.open(Native Method)
        at java.io.FileInputStream.<init>(Unknown Source)
        at sun.jkernel.DownloadManager.getBundleURLs(Unknown Source)
        at sun.jkernel.Bundle.getURL(Unknown Source)
        at sun.jkernel.Bundle.download(Unknown Source)
        at sun.jkernel.Bundle.install(Unknown Source)
        at sun.jkernel.Bundle.install(Unknown Source)
        at sun.jkernel.Bundle$2.run(Unknown Source)
        at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(Unknown Source
)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
        at java.lang.Thread.run(Unknown Source)
Exception in thread "Thread-0"

How to reproduce:
Start Control Panel (or any Application ) , javaws notepad.jnlp , swingset etc at the same time.