Yes, this is a known problem.
Basically, the rubebrband included with the script (1.5.0) doesn’t work very well with anything below OSX 10.6.
Try either manually upgrading or downgrading the binary? The file to replace will be located at:
/Users//Library/Preferences/Renoise/V2.7.2/Scripts/Tools/com.renoise.Rubberband.xrnx/bin/osx