I've had some time to work though this problem and thought I'd share what I've discovered.  I started 
out having trouble with a form essentially becoming uneditable.  That is, changes to the form would not 
be written to the protected regions of the .java file as expected.  After reconstructing the form in the 
form builder 3+ times, I discovered the ~/.netbeans/5.0/var/log/message.log file made reference to 
the java.lang.IllegalStateException: Error getting property value.  Upon further investigation, I found 
that the JComboBox in my corrupted form was reporting an error in finding it's minimumSize and it's 
preferredSize.  Once this error occurs, further editing of my form is ineffective.  Upon inspection of the 
.form file, I noticed that these two Properties were missing.  My solution was to duplicate the 
maximumSize property as minimumSize and preferredSize for the JComboBox in the .form file and the 
form became editable again using netbeans.

Another possibly related problem is that if one of my components is selected when clicking the build 
and run icon in the toolbar, then the save hangs and the build never runs.  Clicking away from all 
components and clicking the build and run icon in the toolbar again completes a save, build and run as 
expected.  Perhaps the corruption in the .form file stems from this incomplete save problem.

	Product Version: NetBeans IDE 5.0 (Build 200601251500)
	Operating System: Mac OS X version 10.3.9 running on ppc
	Java: 1.4.2_09

Hope that helps the coders find the bug and the users work around the problem until it is resolved.