is it reproducible?
Petre, could you try it on Vista?

krystyne, where you get the build from? What distro?

Product Version: NetBeans IDE Dev (Build 200807101204)
Java: 1.6.0_10-beta; Java HotSpot(TM) Client VM 11.0-b11
System: Windows Vista version 6.0 running on x86; Cp1250; cs_CZ (nb)
Userdir: C:\Users\Petr\.netbeans\dev

I was unable to reproduce it with this build (I played with JSP debugging before IDE shutdown).

This was the zip build - javaee 
NetBeans IDE Dev (Build 20080711151305)
JDK 1.6.0_03
Windows Vista version 6.0

I still have the machine in the crrent state if you wanted
to look at it. I closed the IDE in the middle of a client-side
only debugging session with web project. I can't say if I can 
reproduce it. Please contact me via email to get access to machine.

I'm seeing the same thing on Ubuntu 8.04 with JDK1.6b10 on the daily 07/17 build: I had the IDE running and tried to
quit without saving a file.  The IDE offered to save the file for me first - which I accepted.  The IDE exited.  Now I
can't start it again.  I get the same error when I run from command-line:
twolf@beowulf:~$ netbeans
-------------------------------------------------------------------------------
>Log Session: Thursday, July 17, 2008 2:16:16 PM EDT
>System Info: 
  Product Version         = NetBeans IDE Dev (Build 200807170007)
  Operating System        = Linux version 2.6.24-19-generic running on i386
  Java; VM; Vendor        = 1.6.0_10-beta; Java HotSpot(TM) Client VM 11.0-b12; Sun Microsystems Inc.
  Runtime                 = Java(TM) SE Runtime Environment 1.6.0_10-beta-b25
  Java Home               = /opt/java/jdk1.6.0_10/jre
  System Locale; Encoding = en_US (nb); UTF-8
  Home Directory          = /home/twolf
  Current Directory       = /home/twolf
  User Directory          = /home/twolf/.netbeans/dev
  Installation            = /opt/java/netbeans/nb6.1
                            /opt/java/netbeans/ide9
                            /opt/java/netbeans/java2
                            /opt/java/netbeans/apisupport1
                            /opt/java/netbeans/websvccommon1
                            /opt/java/netbeans/profiler3
                            /opt/java/netbeans/gsf1
                            /opt/java/netbeans/harness
                            /opt/java/netbeans/platform8
  Boot & Ext. Classpath   =
/opt/java/jdk1.6.0_10/jre/lib/resources.jar:/opt/java/jdk1.6.0_10/jre/lib/rt.jar:/opt/java/jdk1.6.0_10/jre/lib/sunrsasign.jar:/opt/java/jdk1.6.0_10/jre/lib/jsse.jar:/opt/java/jdk1.6.0_10/jre/lib/jce.jar:/opt/java/jdk1.6.0_10/jre/lib/charsets.jar:/opt/java/jdk1.6.0_10/jre/classes:/opt/java/jdk1.6.0_10/jre/lib/ext/sunjce_provider.jar:/opt/java/jdk1.6.0_10/jre/lib/ext/localedata.jar:/opt/java/jdk1.6.0_10/jre/lib/ext/dnsns.jar:/opt/java/jdk1.6.0_10/jre/lib/ext/sunpkcs11.jar
  Application Classpath   =
/opt/java/netbeans/platform8/lib/boot.jar:/opt/java/netbeans/platform8/lib/org-openide-modules.jar:/opt/java/netbeans/platform8/lib/org-openide-util.jar:/opt/java/jdk1.6.0_10/lib/dt.jar:/opt/java/jdk1.6.0_10/lib/tools.jar
  Startup Classpath       =
/opt/java/netbeans/platform8/core/org-openide-filesystems.jar:/opt/java/netbeans/platform8/core/core.jar:/opt/java/netbeans/nb6.1/core/org-netbeans-upgrader.jar:/opt/java/netbeans/nb6.1/core/locale/core_nb.jar
-------------------------------------------------------------------------------
java.nio.BufferUnderflowException
	at java.nio.DirectByteBuffer.get(DirectByteBuffer.java:221)
	at java.nio.ByteBuffer.get(ByteBuffer.java:675)
	at org.netbeans.core.startup.layers.BinaryFS.<init>(BinaryFS.java:137)
	at org.netbeans.core.startup.layers.BinaryCacheManager.load(BinaryCacheManager.java:74)
	at org.netbeans.core.startup.layers.ModuleLayeredFileSystem.loadCache(ModuleLayeredFileSystem.java:151)
	at org.netbeans.core.startup.layers.ModuleLayeredFileSystem.<init>(ModuleLayeredFileSystem.java:114)
	at org.netbeans.core.startup.layers.ModuleLayeredFileSystem.<init>(ModuleLayeredFileSystem.java:110)
	at org.netbeans.core.startup.layers.SystemFileSystem.create(SystemFileSystem.java:350)
	at org.netbeans.core.startup.layers.SessionManager.create(SessionManager.java:96)
	at org.netbeans.core.startup.NbRepository.createDefaultFileSystem(NbRepository.java:138)
	at org.netbeans.core.startup.NbRepository.<init>(NbRepository.java:66)
	at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
	at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39)
	at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)
	at java.lang.reflect.Constructor.newInstance(Constructor.java:513)
	at java.lang.Class.newInstance0(Class.java:355)
	at java.lang.Class.newInstance(Class.java:308)
	at org.openide.util.lookup.MetaInfServicesLookup$P.getInstance(MetaInfServicesLookup.java:431)
	at org.openide.util.lookup.AbstractLookup.lookup(AbstractLookup.java:415)
	at org.openide.util.lookup.ProxyLookup.lookup(ProxyLookup.java:205)
	at org.openide.filesystems.ExternalUtil.initialize(ExternalUtil.java:154)
	at org.openide.filesystems.ExternalUtil.getRepository(ExternalUtil.java:71)
	at org.openide.filesystems.Repository.getDefault(Repository.java:155)
	at org.netbeans.core.startup.Main.start(Main.java:313)
	at org.netbeans.core.startup.TopThreadGroup.run(TopThreadGroup.java:110)
	at java.lang.Thread.run(Thread.java:619)
Cannot add System filesystem, exiting...
twolf@beowulf:~$ 

I'm experiencing this issue after Issue 140672

this looks nasty - IDE won't start up anymore.
Does it happen when you start up NB with fresh userdir? use --userdir command line switch.
Is it reproducible? If it is reproducible only with the "old" userdir then zip it and email it to me.

thank you

*** Issue 140630 has been marked as a duplicate of this issue. ***

I believe this is related to 140061

*** Issue 140746 has been marked as a duplicate of this issue. ***

Yes, restarting with a fresh userdir allows IDE startup again. Attaching my
original userdir.

Created attachment 64982 [details]
userdir

Jirko, related to the P1 about dtd.

*** This issue has been marked as a duplicate of 140061 ***