halionone can't find audio samples

Hi all,
I’ve just updated from cubase 4.0.1 to cubase 4.5.2 and halion no longer works. I get the following message:
Some audio files could not be found
content seems to be broken
It appears that from 4.1 onwards Halion One is a separate install. Its no longer contained in the main cubase app file. That’s fine, so I did an install of the separate package but it hasn’t helped. I did the Locate Contents thing from the HalionOne player, and I can see that the halion defaults.xml file shows the correct file location of the .hsb files. But every time I try and use halion I get that annoying message and no sounds will play.
I’ve spent hours trawling the knowledgebase and the forums but nothing I’ve tried has helped. So this is my last resort.
Any suggestions will be greatly appreciated.