+1  A: 

Ok, looks like this is a problem with the version of xdebug that I was using. Xdebug 2.1.0 beta has a new pseudo-property called CLASSNAME that Netbeans doesn't quite know how to handle yet. I was able to get around this by using xdebug 2.0.5.

In case someone is interested:
Here is the Netbeans bug report: http://netbeans.org/bugzilla/show_bug.cgi?id=182148.
And here is the xdebug bug report: http://bugs.xdebug.org/view.php?id=518

sdek