I don't use lightroom, James (just PS), but I did noticed after the last big update my old apps were left behind (PS & Bridge) and needed to click 'Uninstall' from the Adobe desktop thingy. May help perhaps? I suspect your old version of lightroom is the other app that has it open. Cheers.
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Ooops, I walked away half way through typing this and see you now have it sorted.