Created attachment 164232 [details]
messages.log - the dialog asked me to attach this file

Previously it used to happen almost exclusively while debugging. My project is a Java web project and I've enabled incremental debugging (in order to see the effects of changes in my mode almost immediately). Pushing the "Apply Code Changes", if I remember, used to trigger this error sometimes. But now my impression is it happens all the time, even when not debugging / running. A random dialog with this annoying alert will appear, and then nothing stops it from appearing one and one and another time again, usually just after having closed the previous one, thus killing productivity. Then apparently the error can spontaneously disappear and leave you alone for a while, or keep there forever and a restart is necessary, crossing for fingers hoping it won't happen again.

This is the content of the dialog:

"Random 'Unexpected Exception' Dialog:
A java.lang.NullPointerException exception has ocurred.
Please report this at http://www.netbeans.org/community/issues.html,
including a copy of your messages.log file as an attachment.
The messages.log files is located in your 
(path)"

It could be that the main triggering session were having started a debugging session; I don't know at all.

I would say I started noticing this much more frequently after I started using dev versions from the two last months ago (that I downloaded for overcoming some other annoying bugs).

My setup is a multimonitor one. Although at this momment Netbeans only occupies one. 

When this error happens, no matter if I click "cancel" or whatever on the dialog, the IDE becomes unresponsive:
buttons can be "hovered" and they react "visually" to the state, but do nothing when clicked. I discovered that,
if I select one menú options from the vertical top var, buttons become responsive again. 

But it's very annoying as error dialogs would come and come again, preventing you from working.