So this is a classic no-context "it's broken, I don't know what I did" whine/question/beg for help.
I must have installed a build script for ghc (my memory is terrible these days) and left it unconfigured. Now ST refuses to start unless it gets its mod-ghc with a correct path etc. etc. And won't start. It's still resident in the windows task manager, and one must force-end its task so it can tell me again it wants its mod-ghc.
So I'm thinking "I don't have time for this stuff right now", uninstall ST, download it again, install and it's still broken. I've been pouring through the file system with a fine comb but can't seem to find any of the files referenced in SublimePlugin.py or PackageSetup.py, let alone the configuration to disable its crush on mod-ghc.