Weird SVN State

Today when I got to work and tried to sync a pile of my projects, I was met with the following exception (and a cute dialog telling me the same thing, but without as many red X's):

org.eclipse.team.svn.core.connector.SVNConnectorException: svn: '/home/mrennie/workspaces/workspace/CommandLineDebugger' is not a working copy
svn: Cannot read from '/home/mrennie/workspaces/workspace/CommandLineDebugger/.svn/format': /home/mrennie/workspaces/workspace/CommandLineDebugger/.svn/format (No such file or directory)
at org.polarion.team.svn.connector.svnkit.SVNKitConnector.handleClientException(SVNKitConnector.java:1400)
at org.polarion.team.svn.connector.svnkit.SVNKitConnector.status(SVNKitConnector.java:337)
at org.eclipse.team.svn.core.extension.factory.ThreadNameModifier.status(ThreadNameModifier.java:608)
at org.eclipse.team.svn.core.operation.local.RemoteStatusOperation$2.run(RemoteStatusOperation.java:147)
at org.eclipse.team.svn.core.utility.ProgressMonitorUtility.doSubTask(ProgressMonitorUtility.java:118)
at org.eclipse.team.svn.core.operation.AbstractActionOperation.protectStep(AbstractActionOperation.java:154)
at org.eclipse.team.svn.core.operation.AbstractActionOperation.protectStep(AbstractActionOperation.java:149)
at org.eclipse.team.svn.core.operation.local.RemoteStatusOperation.runImpl(RemoteStatusOperation.java:145)
at org.eclipse.team.svn.core.operation.AbstractActionOperation.run(AbstractActionOperation.java:81)
at org.eclipse.team.svn.core.utility.ProgressMonitorUtility.doTask(ProgressMonitorUtility.java:104)
at org.eclipse.team.svn.core.operation.CompositeOperation.runImpl(CompositeOperation.java:95)
at org.eclipse.team.svn.core.operation.AbstractActionOperation.run(AbstractActionOperation.java:81)
at org.eclipse.team.svn.core.operation.LoggedOperation.run(LoggedOperation.java:39)
at org.eclipse.team.svn.core.utility.ProgressMonitorUtility.doTask(ProgressMonitorUtility.java:104)
at org.eclipse.team.svn.core.utility.ProgressMonitorUtility.doTaskExternal(ProgressMonitorUtility.java:90)
at org.eclipse.team.svn.core.synchronize.AbstractSVNSubscriber.findChanges(AbstractSVNSubscriber.java:314)
at org.eclipse.team.svn.core.synchronize.AbstractSVNSubscriber$UpdateStatusOperation$2.run(AbstractSVNSubscriber.java:349)
at org.eclipse.team.svn.core.utility.ProgressMonitorUtility.doSubTask(ProgressMonitorUtility.java:118)
at org.eclipse.team.svn.core.operation.AbstractActionOperation.protectStep(AbstractActionOperation.java:154)
at org.eclipse.team.svn.core.operation.AbstractActionOperation.protectStep(AbstractActionOperation.java:149)
at org.eclipse.team.svn.core.synchronize.AbstractSVNSubscriber$UpdateStatusOperation.runImpl(AbstractSVNSubscriber.java:347)
at org.eclipse.team.svn.core.operation.AbstractActionOperation.run(AbstractActionOperation.java:81)
at org.eclipse.team.svn.core.operation.LoggedOperation.run(LoggedOperation.java:39)
at org.eclipse.team.svn.core.utility.ProgressMonitorUtility.doTask(ProgressMonitorUtility.java:104)
at org.eclipse.team.svn.core.utility.ProgressMonitorUtility.doTaskExternal(ProgressMonitorUtility.java:90)
at org.eclipse.team.svn.core.utility.ProgressMonitorUtility.doTaskExternal(ProgressMonitorUtility.java:81)
at org.eclipse.team.svn.core.synchronize.AbstractSVNSubscriber.refresh(AbstractSVNSubscriber.java:186)
at org.eclipse.team.svn.core.synchronize.UpdateSubscriber.refresh(UpdateSubscriber.java:73)
at org.eclipse.team.core.subscribers.Subscriber.refresh(Subscriber.java:466)
at org.eclipse.team.core.subscribers.SubscriberMergeContext.refresh(SubscriberMergeContext.java:85)
at org.eclipse.team.core.mapping.provider.SynchronizationContext.refresh(SynchronizationContext.java:109)
at org.eclipse.team.internal.ui.synchronize.RefreshModelParticipantJob.doRefresh(RefreshModelParticipantJob.java:69)
at org.eclipse.team.internal.ui.synchronize.RefreshParticipantJob.run(RefreshParticipantJob.java:309)
at org.eclipse.team.internal.ui.synchronize.RefreshModelParticipantJob.run(RefreshModelParticipantJob.java:117)
at org.eclipse.core.internal.jobs.Worker.run(Worker.java:54)
Caused by: org.tigris.subversion.javahl.ClientException: svn: '/home/mrennie/workspaces/workspace/CommandLineDebugger' is not a working copy
svn: Cannot read from '/home/mrennie/workspaces/workspace/CommandLineDebugger/.svn/format': /home/mrennie/workspaces/workspace/CommandLineDebugger/.svn/format (No such file or directory)
at org.tigris.subversion.javahl.JavaHLObjectFactory.throwException(JavaHLObjectFactory.java:724)
at org.tmatesoft.svn.core.javahl.SVNClientImpl.throwException(SVNClientImpl.java:1929)
at org.tmatesoft.svn.core.javahl.SVNClientImpl.status(SVNClientImpl.java:304)
at org.tmatesoft.svn.core.javahl.SVNClientImpl.status(SVNClientImpl.java:282)
at org.polarion.team.svn.connector.svnkit.SVNKitConnector.status(SVNKitConnector.java:334)
... 33 more
Caused by: org.tmatesoft.svn.core.SVNException: svn: '/home/mrennie/workspaces/workspace/CommandLineDebugger' is not a working copy
svn: Cannot read from '/home/mrennie/workspaces/workspace/CommandLineDebugger/.svn/format': /home/mrennie/workspaces/workspace/CommandLineDebugger/.svn/format (No such file or directory)
at org.tmatesoft.svn.core.internal.wc.SVNErrorManager.error(SVNErrorManager.java:64)
at org.tmatesoft.svn.core.internal.wc.admin.SVNAdminAreaFactory.open(SVNAdminAreaFactory.java:149)
at org.tmatesoft.svn.core.internal.wc.admin.SVNWCAccess.doOpen(SVNWCAccess.java:355)
at org.tmatesoft.svn.core.internal.wc.admin.SVNWCAccess.open(SVNWCAccess.java:263)
at org.tmatesoft.svn.core.internal.wc.admin.SVNWCAccess.open(SVNWCAccess.java:256)
at org.tmatesoft.svn.core.internal.wc.admin.SVNWCAccess.openAnchor(SVNWCAccess.java:151)
at org.tmatesoft.svn.core.wc.SVNStatusClient.doStatus(SVNStatusClient.java:320)
at org.tmatesoft.svn.core.javahl.SVNClientImpl.status(SVNClientImpl.java:300)
... 35 more

After swearing for a bit and asking Google what I should do (and having no luck) I tried deleting suspicious looking files from the /.svn folder located in each affected project. The winner - at least for me - was to delete the /.svn/tmp folder and all of its contents and then restart Eclipse. After that all is well and I can sync to my hearts content.

I filed a bug for this state problem here:
https://bugs.eclipse.org/bugs/show_bug.cgi?id=328258