Nope... I've been fairly lucky this time around - the last install was over 2 years ago...
Fixed it anyway. After many hours poking around under the hood, I finally spotted three "handles" from "Addon Scenery" in the task manager. The last time I tried opening a bgl with Instant Scenery and got the 6% bug, I ran windows task manager and saw that thing called the resource monitor. "Resource Monitor" I thinks to myself, "Let's see what this shows..."
I looked at all odd things that you can see there and finally came across a tab called "CPU" with processes, services, associated handles and associated modules as part of the window.
After a couple of hours I noticed you could sort and search the various lists. I finally had the idea of using "Addon Scenery" as a search term and ONLY three "handles" came up - PF23 (Yes, mine) the FSHeliCH Lama helicopter summer sceneries and PF20 Misty's place.
I deactivated all three in FSX library and lo and behold, Instant scenery woke up and allowed me to open the new eagleskinner location bgls for editing.
What's happening, apparently, is that FSX is looking for an object in those three addon sceneries and not finding it because I haven't got it or . It was too late for me to investigate any more this morning (1:00 a.m.), but I have been tidying out and up in the new Eagleskinner strip area since, adding easter egg goodies all over the place.
I restored the three culprits one at a time and did some Instant scenery work. Misty's - good. Daredevils - good. CHheli Lama Switzerland scenery addins... AHA!! I still have the sceneries active in the addon scenery folder, but the last install was probably corrupted. I think the two moorings sceneries were just innocent bystanders.
The only reason I assume that the addon sceneries are causing the stress was that I have several hundred of them and only three were showing in the task manager as being active (or troublesome?).
This could all be hot air, but the problem appears to have lifted and I haven't done anything else to my PC these past few days. Incidentally, I had also been having issues lately in not getting from the scenery library to the free flight library in the FSX startup menus. With Lama X sceneries off, that works again too.