The general problem is that in several situations, error icons in the Projects/Files tree view keep sticking although 
the source files don't contain errors (any more), and there's no way to manually reset them for a source tree (as 
opposed to for a single source file).

One situation appears to be certain kinds of circular source code dependencies (possibly involving generics). This is 
similar to how you can get errors when compiling source files one by one, but compilation is successful when compiling 
the complete set of source files in a single javac call. (Unfortunately I can't provide a succinct source code example 
of this, but I have a largish project where this happens all the time for a certain set of dependent source files.)

The other situation is multiple projects and/or not catching updates of a JAR in the classpath. I regularly work in a 
multi-project setting (J2EE, several EAR projects with several EJB/WAR sub-projects). Each project source tree has its 
own corresponding CVS module. Some of the projects have the ouput JAR of some other project in their classpath (Project 
Properties -> LibrarieS). What usually happens is that I update several of the projects from CVS, which causes error 
icons in at least one project, because it doesn't see the required changes in the other project yet (or possibly also 
because it starts re-compiling files while CVS is still running?). Or I update just one project, causing compile 
errors, then notice because of the errors that I also need the updates of some other dependent project, get those 
updates, compile the other project, but the error icons on the first project still persist.

Now to my actual point. Of course it would be great if the error icons would go away automatically (or not appear at 
all where possible), but I understand that the issues and dependencies are complicated, so I don't hold my breath that 
this will ever work perfectly. BUT:

There ought to be a way to clear the error icons and/or have them recalculated for a source (sub-)tree. Currently the 
only way to get rid of them, besides closing the IDE and deleting the cache, is to open each single "erroneous" source 
file in the editor and close it again (or rather: switch to a different source file, which is what seems to trigger the 
updating of the error icon). Even a successful clean build doesn't clear the error icons.

As a minor point, it would be nice if the error icons would be better synchronized with the little error/warning 
indicator at the top of the editor's right edge. When that indicator changes from red to green (or yellow), the error 
icon in the treeview still doesn't go away. One has to open a different source file for the error icon to be updated.

Product Version: NetBeans IDE 6.0 (Build 200711261600)
Java: 1.6.0_02; Java HotSpot(TM) Client VM 1.6.0_02-b05
System: Windows XP version 5.1 running on x86; Cp1252; en_US (nb)