Question: **The Problem**

When I start Netbeans, it tells me that 21 updates have been found, and I have clickable action to update the IDE:
![Click here to make your IDE up to date.](https://i.stack.imgur.com/TvRcj.png)
![Netbeans IDE Installer](https://i.stack.imgur.com/BmQEr.png)

The install fails and gives me these messages:
![Unable to connect to the Update Center](https://i.stack.imgur.com/CTfSW.png)
![http://updates.netbeans.org/netbeans/updates/8.0/uc/final/distribution/patch11/ide/org-netbeans-libs-svnClientAdapter-svnkit.nbm Not all of the plugins have been successfully downloaded. The server may be unavailable at the moment. Try again later.](https://i.stack.imgur.com/SGUnW.png)

**What I've Tried**

* Disabled anti-virus (AVG)
* Disabled Windows Firewall
* Added Netbeans 8.0 to be allowed by the firewall

**Other**

* Windows 7 - 64 bit

Answer: 
Turns out it was Norton Family that was blocking the connection. My network admin had to disable it temporarily so I could do the IDE update.
Netbeans seems to fail the whole update process if there is some temporary network problem when downloading some plugin. It was probably your case to and when you retry the update it simply worked (not really having anything to do with your AntiVirus Software).

I had to upgrade from full edition Netbeans 8.0 to 8.0.2 and managed to do that by simply re-trying several times. Not sure if that is important by I updated through Tools -> Plugins and use Update button. I then hit "Try again" every time the download failed.

For anyone with a similar problem you can follow [Bug 249791 - Retry should only download missing plugins](https://netbeans.org/bugzilla/show_bug.cgi?id=249791).