Useful tip, Dave, thanks. I had to uninstall (manually) my copy of HalionSonic (full version) just to be able to open the couple of projects with it in them.
If the problem lies in the eLicenser, you might think Steinberg would chip in with this information? I wonder how many people have been seriously inconvenienced by installing the wretched HSO demo?
(Edited to say that there doesn’t seem to be any way of completely removing the licence using the eLicenser panel. I found that the HSO demo license was shown in red. I used “Validate license usage periods” and found this resulted in the HSO license becoming greyed out. Hopefully that will fix the problem. I’m now re-installing HS, which I haven’t used for weeks since this problem happened.)