xpinc Javascript no longer works after client downgrade

xpinc Javascript no longer works after client downgrade

I needed to downgrade my Lotus Notes client from 8.5.3 to 8.5.2 to verify
some functionality works in the earlier client. After doing this, any
JavaScript included in my XPages, from a simple alert() prompt to the
loading of Dojo, no longer works. I've completely uninstalled 8.5.2,
rebooted and reinstalled the client, to no avail. Weird thing is,
JavaScript does work in my Notes client in a simple page.
I've double-checked, and my Notes client preferences are set to run
JavaScript, and my ECL entries show every legit signer as being able to
run JavaScript. The databases I've tested so far all have "Use JavaScript
when loading pages" enabled.
Any idea what could be going wrong?