Can't get rid of error warning when opening and closing audio files

I recently upgraded from WaveLab 7 to WaveLab Pro 9 using Windows 10. Every time I open and close an audio file I get the following message:-

An error has occurred. The file could not be written successfully.

I click ok and the message goes away. No such thing happens with OSX so this is obviously a bug with Wavelab on Windows and it slows down my workflow considerably.

Any advice much appreciated.


When closing a file, WaveLab writes this file:
C:\Users[YourName]\AppData\Roaming\Steinberg\WaveLab Pro 9\Cache\lru.txt
Make sure this location or file is not read-only.