Trouble in eclipse: java.lang.ClassCastException

it's been two days that I constantly get an error dialog box every 45 seconds with the title of :

Multiple problems have occurred

and under it says:

java.lang.ClassCastException

and in the details there is a repeated line which says:

org.eclipse.core.internal.dtree.NoDataDeltaNode cannot be cast to org.eclipse.core.internal.dtree.DataTreeNode

here is a picture of it:

I press OK, and continue coding, my code works fine, in both simulator and my mobile, but it's really annoying to see this dialog every minute, or my be even less than a minute!

Maybe your workspace is somehow corrupted. Try to setup a new workspace.

Choose File -> Switch Workspace -> Other from the eclipse menu. Then choose a new directory. You will have to re-import your sources and make all configurations.