It seems this line triggers the errors:
PATH=“$PATH;$RMANTREE/bin”
This one does no harm:
HOUDINI_DEFAULT_RIB_RENDERER=prman21.3
And I have left out defining RMANTREE in the houdini.env file as I already have it setup from the RenderMan installation.
@Tom
Good to know, I was thinking of trying out the Qt4 version but didn't have the time.