Glad, you've managed to find a workaround.
I think the files are loaded from NVidia's repo when you install Corona and they stay like that on the disk (they don't get updated with new CUDA/OPTIX releases, which are more frequent than Corona updates). Maybe if installation process is run again...
5min later ... Yup, if you'd run installation again, new/latest files get downloaded from NVidia:
cudart64_90.dll
cudnn64_7.dll
optix.6.0.0.dll
optix_denoiser.6.0.0.dll
So, note: after updating drivers, update NVidia Denoiser by running Corona Installation/update!
Anyways, feels good to find solution by yourself.
:)