Hey, so I've recently run into this problem when using Windower 4.0 and I'm at a loss on how to fix it.
Windower has been working fine for the past months for me without a hitch. There was the December patch update on Thursday the 10th, some plugins broke (as I'm sure you're all aware) but that was nothing too surprising -- I was still able to play using Windower. It wasn't until yesterdays (Friday, Dec. 11th) automatic update to Windower that I've been unable to boot POL through Windower without it crashing instantly (as shown in the screenshot below). I noticed that in that update on Friday, Windower auto-downloaded some Item descriptions among other things, maybe one of those updated files are the cause for this?
I've tried a variety of solutions. I tried completely uninstalling FFXI/POL/Windower overnight and reinstalling from scratch, removing all addons/plugins, and changing regions (from auto-detect to NA). I also tried using the Development Build of Windower, as well as tried running both Windower and POL in Compatibility mode... the problem still persists
Should also be noted that I can still boot and run the game completely fine without Windower.