Thanks to both.
I uninstalled Impulse, and as the Stardock Store is reporting the correct expiry, I'll assume it's smooth sailing for now.
I sincerely hope you uninstalled all your Stardock stuff with Impulse first?
If not, install Impulse, uninstall all SD stuff with it, starting with WB (Very Important), then uninstall Impulse, run CCleaner or the like, reboot.
Install SDC, install all SD things available via SDC, then get the rest from the store.
I should have said this earlier.