Turning off PresentMon support didn't help unfortunately - I was actually lucky to be able to turn it off, the app lasted long enough for me to get into the menus to change it. I actually think the crash may not have happened in that run. But I quit and restarted, and it died after a couple of seconds as usual. In an effort to see how consistent it is, I ran five more times - it crashed each time. One of these times I tried to get into the menus again, and I got only as far as the initial dialog before the app crashed. Strange one. At least I can run outside of Program Files without it crashing though, so that's fine for some kind of monitoring (I use HWInfo mainly for the OSD though - I want to stay as Arm native as possible so am avoiding things like x64 RTSS).
EDIT - forget that last part, it now crashes when run outside of Program Files also, so must have been a one-off when it worked before.