Do not import media when loading the XML (there is a checkbox for this), and add the DPX files to the media pool just as you would do for a EDL conform. Then all the matching is done based on reel number and timecode.
Are you running the v8 release from the BMD website? Please re install the official release and if you continue to have problems, please send your Mac system profiler XML output as well as resolve logs to our support. Don’t forget to send your dongle ID for verification.
If the R3D files are truncated for whatever reason, they take a very long to open as the Red SDK needs to scan through the file to detect the length of the clip. Perhaps this could be causing the problem.