20110606-cec0d10d4352. When I try running the IDE with its installation and projects on VBox share (userdir on local drive), I get hundreds of stack traces in the console like this:

WARNING [org.netbeans.modules.masterfs.watcher.Watcher]: Cannot add filesystem watch for E:/.../src/main/webapp
INFO [org.netbeans.modules.masterfs.watcher.Watcher]: Exception
java.io.IOException: wrong path
        at org.netbeans.modules.masterfs.watcher.WindowsNotifier.addWatch(WindowsNotifier.java:299)
        at org.netbeans.modules.masterfs.watcher.WindowsNotifier.addWatch(WindowsNotifier.java:71)
[catch] at org.netbeans.modules.masterfs.watcher.Watcher$Ext.register(Watcher.java:237)
        at org.netbeans.modules.masterfs.watcher.Watcher.register(Watcher.java:119)
        at org.netbeans.modules.masterfs.filebasedfs.fileobjects.BaseFileObj.addFileChangeListener(BaseFileObj.java:479)
        at org.netbeans.modules.web.core.jsploader.JspDataObject$Listener.register(JspDataObject.java:464)
        at org.netbeans.modules.web.core.jsploader.JspDataObject$Listener.access$100(JspDataObject.java:456)
        at org.netbeans.modules.web.core.jsploader.JspDataObject.initialize(JspDataObject.java:237)
        at org.netbeans.modules.web.core.jsploader.JspDataObject.<init>(JspDataObject.java:134)
        at org.netbeans.modules.web.core.jsploader.JspLoader.createJspObject(JspLoader.java:126)
        at org.netbeans.modules.web.core.jsploader.JspLoader.createMultiObject(JspLoader.java:132)
        at org.openide.loaders.MultiFileLoader.handleFindDataObject(MultiFileLoader.java:145)
        at org.openide.loaders.DataObjectPool.handleFindDataObject(DataObjectPool.java:161)
        at org.openide.loaders.DataLoader.findDataObject(DataLoader.java:407)
        at org.openide.loaders.DataLoader.findDataObject(DataLoader.java:380)
        at org.openide.loaders.DataLoaderPool.findDataObject(DataLoaderPool.java:535)
        at org.openide.loaders.DataLoaderPool.findDataObject(DataLoaderPool.java:493)
        at org.openide.loaders.DataObject.find(DataObject.java:523)
        at org.netbeans.modules.parsing.api.Source.getDocument(Source.java:241)
        at org.netbeans.modules.html.editor.hints.HtmlHintsProvider$AbstractErrorChecksForMimetypeFix.<init>(HtmlHintsProvider.java:486)
        at org.netbeans.modules.html.editor.hints.HtmlHintsProvider$EnableErrorChecksForMimetypeFix.<init>(HtmlHintsProvider.java:531)
        at org.netbeans.modules.html.editor.hints.HtmlHintsProvider.computeErrors(HtmlHintsProvider.java:227)
        at org.netbeans.modules.html.editor.HtmlErrorFilter.filter(HtmlErrorFilter.java:96)
        at org.netbeans.modules.csl.core.ErrorFilterQuery.getFilteredErrors(ErrorFilterQuery.java:67)
        at org.netbeans.modules.csl.core.TLIndexerFactory$TLIndexer.index(TLIndexerFactory.java:241)
        at org.netbeans.modules.parsing.spi.indexing.Indexable$MyAccessor$3.run(Indexable.java:186)
        at org.netbeans.modules.parsing.impl.indexing.RepositoryUpdater.runIndexer(RepositoryUpdater.java:271)
        at org.netbeans.modules.parsing.spi.indexing.Indexable$MyAccessor.index(Indexable.java:184)
        at org.netbeans.modules.parsing.impl.indexing.RepositoryUpdater$Work$3.run(RepositoryUpdater.java:2139)
        at org.netbeans.modules.parsing.impl.indexing.RepositoryUpdater$Work$3.run(RepositoryUpdater.java:2156)
        at org.netbeans.modules.parsing.impl.TaskProcessor.callUserTask(TaskProcessor.java:649)
        at org.netbeans.modules.parsing.api.ParserManager$UserTaskAction.run(ParserManager.java:154)
        at org.netbeans.modules.parsing.api.ParserManager$UserTaskAction.run(ParserManager.java:138)
        at org.netbeans.modules.parsing.impl.TaskProcessor$2.call(TaskProcessor.java:217)
        at org.netbeans.modules.parsing.impl.TaskProcessor$2.call(TaskProcessor.java:214)
        at org.netbeans.modules.masterfs.filebasedfs.utils.FileChangedManager.priorityIO(FileChangedManager.java:168)
        at org.netbeans.modules.masterfs.providers.ProvidedExtensions.priorityIO(ProvidedExtensions.java:356)
        at org.netbeans.modules.parsing.impl.Utilities.runPriorityIO(Utilities.java:71)
        at org.netbeans.modules.parsing.impl.TaskProcessor.runUserTask(TaskProcessor.java:214)
        at org.netbeans.modules.parsing.api.ParserManager.parse(ParserManager.java:106)
        at org.netbeans.modules.parsing.impl.indexing.RepositoryUpdater$Work.indexEmbedding(RepositoryUpdater.java:2106)
        at org.netbeans.modules.parsing.impl.indexing.RepositoryUpdater$Work.doIndex(RepositoryUpdater.java:1949)
        at org.netbeans.modules.parsing.impl.indexing.RepositoryUpdater$Work.access$1400(RepositoryUpdater.java:1596)
        at org.netbeans.modules.parsing.impl.indexing.RepositoryUpdater$Work$2.run(RepositoryUpdater.java:1776)
        at org.netbeans.modules.parsing.impl.indexing.RepositoryUpdater$Work$2.run(RepositoryUpdater.java:1774)
        at org.netbeans.modules.parsing.impl.indexing.errors.TaskCache.refreshTransaction(TaskCache.java:460)
        at org.netbeans.modules.parsing.impl.indexing.RepositoryUpdater$Work.index(RepositoryUpdater.java:1774)
        at org.netbeans.modules.parsing.impl.indexing.RepositoryUpdater$AbstractRootsWork.scanSource(RepositoryUpdater.java:3596)
        at org.netbeans.modules.parsing.impl.indexing.RepositoryUpdater$AbstractRootsWork.scanSources(RepositoryUpdater.java:3499)
        at org.netbeans.modules.parsing.impl.indexing.RepositoryUpdater$RootsWork.getDone(RepositoryUpdater.java:3244)
        at org.netbeans.modules.parsing.impl.indexing.RepositoryUpdater$Work.doTheWork(RepositoryUpdater.java:2255)
        at org.netbeans.modules.parsing.impl.indexing.RepositoryUpdater$Task._run(RepositoryUpdater.java:4015)
        at org.netbeans.modules.parsing.impl.indexing.RepositoryUpdater$Task.run(RepositoryUpdater.java:3955)
        at org.netbeans.modules.parsing.impl.TaskProcessor.callParserResultTask(TaskProcessor.java:624)
        at org.netbeans.modules.parsing.impl.TaskProcessor$CompilationJob.run(TaskProcessor.java:734)
        at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:441)
        at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:303)
        at java.util.concurrent.FutureTask.run(FutureTask.java:138)
        at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
        at java.lang.Thread.run(Thread.java:619)

The one-line warnings I could tolerate, but not the stack traces.