Resolved SORT OF, but not to my satisfaction.
I discovered that I had an entry in my repository for GIMP 2.8 -- something containing "kesselgulasch" I vaguely recall adding this so that I could get v 2.8 while the official repository only offered 2.6. I was tired of waiting around for 2.8 when a four year old version 2.6 was still the only official offering.
So apparently a subsequent MintUpdate changed some libs (or who knows what) breaking v 2.8. (Hence my sudden will not start problem)
I removed the un-official repository, updated, purged gimp, reinstalled it from software manager and voila - it runs....BUT it is v 2.6
Now according to the GIMP site "Ubuntu or Debian users can simply run apt-get install gimp to get the latest stable release of GIMP. Ubuntu users can also install GIMP from Software Centre." So I should have gotten v 2.8.6, but instead got the old thing GIMP.
Why - and how do I get what should be in the Software Center?