NetBeans could not install some modules
It's very simple :
1 - Try to find this file /home/yourname/.cache/netbeans
2 - And clear all files 
1. Uninstall Net Beans
2. Just Delete everything from:
C:\Users\your_name\AppData\Local\NetBeans\Cache\8.1\C:\Users\your_name\AppData\Roaming\NetBeans\8.1\I am using 8.1 version. 3. After deleting just restart your machine.
4. Re-Install
I did the following steps and it worked :)
I have the same issue. If you will get version 7.4 and install it on a clean PC (or remove all netbeans data/config folders) and disable the check for updates, during installation the installation will proceed without errors and netbeans runs. In the case of the first update, the issue comes back.