While project is created or imported, if it takes long time to be configured and built after it first appears in Package Explorer, it is easy to delete it. I have got a lot of various exceptions, that is an example from WTP:

!ENTRY org.eclipse.wst.validation 4 0 2012-06-22 16:34:40.251
!MESSAGE IWAE0027E Could not retrieve the validation configuration for resource jboss-as-login.
!STACK 0
java.lang.reflect.InvocationTargetException: IWAE0027E Could not retrieve the validation configuration for resource jboss-as-login.
	at org.eclipse.wst.validation.internal.ConfigurationManager.getProjectConfiguration(ConfigurationManager.java:135)
	at org.eclipse.wst.validation.internal.ConfigurationManager.getConfiguration(ConfigurationManager.java:251)
	at org.eclipse.wst.validation.internal.ValManager.getValidatorsNotCached(ValManager.java:226)
	at org.eclipse.wst.validation.internal.ValManager.access$1(ValManager.java:220)
	at org.eclipse.wst.validation.internal.ValManager$ValidatorCache.getValidatorsCached(ValManager.java:1294)
	at org.eclipse.wst.validation.internal.ValManager.getValidators(ValManager.java:197)
	at org.eclipse.wst.validation.internal.ValManager.accept(ValManager.java:745)
	at org.eclipse.wst.validation.internal.ValBuilderJob.run(ValBuilderJob.java:201)
	at org.eclipse.wst.validation.internal.ValBuilderJob.runInWorkspace(ValBuilderJob.java:126)
	at org.eclipse.core.internal.resources.InternalWorkspaceJob.run(InternalWorkspaceJob.java:38)
	at org.eclipse.core.internal.jobs.Worker.run(Worker.java:54)
Caused by: org.eclipse.core.internal.resources.ResourceException: Resource '/jboss-as-login' does not exist.
	at org.eclipse.core.internal.resources.Resource.checkExists(Resource.java:320)
	at org.eclipse.core.internal.resources.Resource.checkAccessible(Resource.java:194)
	at org.eclipse.core.internal.resources.Project.checkAccessible(Project.java:147)
	at org.eclipse.core.internal.resources.Resource.checkAccessibleAndLocal(Resource.java:200)
	at org.eclipse.core.internal.resources.Resource.getSessionProperty(Resource.java:1242)
	at org.eclipse.wst.validation.internal.ConfigurationManager.getProjectConfiguration(ConfigurationManager.java:126)
	... 10 more
Root exception:
org.eclipse.core.internal.resources.ResourceException: Resource '/jboss-as-login' does not exist.
	at org.eclipse.core.internal.resources.Resource.checkExists(Resource.java:320)
	at org.eclipse.core.internal.resources.Resource.checkAccessible(Resource.java:194)
	at org.eclipse.core.internal.resources.Project.checkAccessible(Project.java:147)
	at org.eclipse.core.internal.resources.Resource.checkAccessibleAndLocal(Resource.java:200)
	at org.eclipse.core.internal.resources.Resource.getSessionProperty(Resource.java:1242)
	at org.eclipse.wst.validation.internal.ConfigurationManager.getProjectConfiguration(ConfigurationManager.java:126)
	at org.eclipse.wst.validation.internal.ConfigurationManager.getConfiguration(ConfigurationManager.java:251)
	at org.eclipse.wst.validation.internal.ValManager.getValidatorsNotCached(ValManager.java:226)
	at org.eclipse.wst.validation.internal.ValManager.access$1(ValManager.java:220)
	at org.eclipse.wst.validation.internal.ValManager$ValidatorCache.getValidatorsCached(ValManager.java:1294)
	at org.eclipse.wst.validation.internal.ValManager.getValidators(ValManager.java:197)
	at org.eclipse.wst.validation.internal.ValManager.accept(ValManager.java:745)
	at org.eclipse.wst.validation.internal.ValBuilderJob.run(ValBuilderJob.java:201)
	at org.eclipse.wst.validation.internal.ValBuilderJob.runInWorkspace(ValBuilderJob.java:126)
	at org.eclipse.core.internal.resources.InternalWorkspaceJob.run(InternalWorkspaceJob.java:38)
	at org.eclipse.core.internal.jobs.Worker.run(Worker.java:54)

This problem cannot be cured by even multiple checks in builder/validator, because an object can become inaccessible, though with small probability, in the moment between the check and the attempt to access it. In numerous import/delete and create/delete project operations that I made, I managed to get (rarely) exceptions in CDI builder soon after the check, most often exceptions happen in validation.
This message is automatically generated by JIRA.
If you think it was sent incorrectly, please contact your JIRA administrators.
For more information on JIRA, see: http://www.atlassian.com/software/jira