Hopeful that stuff might be fixed, I uninstalled the "Epic Games launcher" and started again from scratch, this time installing both the launcher and game on C:. It's still happening. There's already a topic on this on the 1st page of the UT bugs forum but it's been there a while with no solution. It's starting to bug me because I can't seem to find my old hard-copy of UT3 so haven't played any UT since upgrading to Windows 10 and I could do with a blast again. (I still have the UT3 install files on my slave drive because I bought a SSD when I upgraded the OS, but it can't launch it because UT3 asks for my key again, which is on the box/manual ).