N360 Toolbar crash in IE11

When I booted up Windows 7 and then opened IE11 all I got was a blank tab and no Norton toolbar.  The favourites bar and command bar where there though.

I waited and waited - nothing.  Then I got that annoying message to disable add-ons to speed up browsing ( I get this a lot).  So I clicked on it.  A small window popped up showing that the Norton toolbar was STILL loading.  So I disabled it and sure enough IE11 loaded up just fine.  I then re-enabled the toolbar and IE11 crashed - I mean really crashed no mouse response at all - couldn't do anything.  I had to restart my PC and this time - luckily - IE11 and the Norton toolbar started just fine.

 

This has happened before and it probably won't be the last time either.  What is causing this and more importantly how do I stop it happening?