After running the latest Windows Update this week I found that IE11 would not start at all. Other browsers started as normal.
After many false leads I finally nailed the issue down to a Logitech service called "process monitor" which was installed with the webcam software. This starts a service by default called LVPrcSrv.exe. After disabling and then re-enabling services using msconfig.exe I finally found that this was the offending culprit. I uninstalled the relevant Logitech software module which I wasn't using anyway and everything works again normally.

I post this now in case it save someone else a few hours of false trails.