1.6.11 IDE wont start

I had some issues with IDE after my PC win7 died.
I reloaded old IDE but was getting lockups.
I downloaded 1.6.11 -(also Im unclear as to what is the latest version of the download available.)
When I start the IDE it loads splash screen and gets to "starting", hangs there for 20seconds or so and then screen just goes away and ide doesnt start up.
There was initially some write to Java bin in windows x86 errors on install. So I reinstalled Java on my machine. and now I can install IDE fine. But as I say it wont start.
I downloaded it on a second laptop in the house- and downloaded fine and installed and started up fine. All in a few minutes as I would expect. Any ideas??
Thanks John D

This may be caused by improperly formatted 3rd party hardware package files used by Boards Manager. This was permitted in previous versions of the Arduino IDE but it causes 1.6.11 to not start. Do you have any URLs entered at File > Preferences > Additional Boards Manager URLs? If so please post them. If you don't know you could use a previous version of the Arduino IDE to check or you can find it in the preferences.txt file at:

On Mac OS X:

On Windows:

On Linux:
/home/(username)/.arduino15 (a.k.a. ~/.arduino15)

It's the line that starts with boardsmanager.additional.urls=

also Im unclear as to what is the latest version of the download available.

Arduino IDE 1.6.11 is the latest release.

I looked in C:\Users(username)\AppData\Local\Arduino15 and can see no such line.
The closest is - board=uno

Im assuming I need to have the IDE open to look at "File > Preferences > Additional Boards Manager URLs?" as you suggested but I cant get the IDE to start, so cant look there.

Try renaming C:\Users(username)\AppData\Local\Arduino15 to C:\Users(username)\AppData\Local\Arduino15backup and start the IDE. Starting the IDE will recreate that folder and thus eliminate the possibility there was anything in the folder causing the problem.

Which version of the Arduino IDE were you using previously?