[Note: There is another thread about this problem but it did not answer the question.]
For one specific project in Eclipse, the problems view does not show errors. It shows warnings but it does not show errors. The other projects do show errors (and everything else). For that problematic project, I can see the red squiggly error line in the files. However, the directory structure does not show an error icon and the error is not populated in the Problems View.
Any ideas?
You'll likely need to change the filter on the Problems view to see the errors. There's a downward pointing arrow in the upper right corner of the panel. Click it -> Configure Contents..., and in the Scope make sure "On any element" is selected.
I'm guessing that the build path for that project is lacking a core library. E.g. if it's a Java project there may not be a JRE/JDK assigned to it.
For a Java project, check this: Properties > Java Build Path > Libraries (this may differ depending on the version of Eclipse, I'm using 3.2.1 at the moment)
There should be a JRE or JDK listed here.
For anyone else who is having this problem, I have found the answer:
Make sure that Eclipse recognizes your project as a Java project. Specifically, under Project Properties ensure that you have a Java Builder that is checked.
That way, your project will be built and you will see errors in the Problems view.
This was my problem: http://solveme.wordpress.com/2009/01/06/eclipse-project-missing-default-java-builder/