I have been having problems with this and Nitro in DP 5. I had Nitro inserted on a track in slot 1 and wanted to add 608 ahead of it. I dragged Nitro down to slot 3, then added 608. DP 5 crashed as the GUI was drawing... I was able to repeat this (a couple of times, unfortunately
). I was able to do what I wanted to by saving the file after moving Nitro where I wanted it, then quitting DP, restarting it and when the file was loaded again, adding 608 in slot 1.
I also found that I must run PSP608 in real time (no pre-rendering), otherwise the buffer will play back whatever was playing when I stopped playback. That is, whenever i restart the tune I'll get a burst of echoed sound (not good!).