Then rescanned VST's and get error 'Main Call' when Sonar tries to scan R-mix.
Also noticed it shows now as 'RMixSonar_64' in browser where it used to read 'R-mix'.  
Might be related to recent installation of NI 'Replika' free reverb plugin.....removed that but still R-mix crashes.
 
Any thoughts would be great, thanks.
 

Sorry not to be much help, but I don't think it can be related to "recent installation of NI 'Replika' free reverb plugin", as I installed that, and R-Mix is still functioning.
 
Hope that you get it sorted.

thanks JB
removed R-mix and re-installed it in X3 from the X2 installation files succesfully 

Glad it's sorted.
 
Out of interest, what do you most use R-Mix for?

now using R-mix for Hiss-noise removal on a finished song.
Just choosing Hiss-noise removal, and setting it to say 1,2 up to 5 does the job usually.
But I could not always do this, sometimes it makes some instruments sound bad....remember 1 time it made the piano part sound bad.
 
and it's handy to isolate and work on a portion of any track/song,
I'll just clone the track, insert R-mix on both tracks, and on 1 I'll put the R-mix fader all down on the isolated part and then I can work on that portion in the other track where I have the fader all up for the portion.