DVD SP 4 is quitting when I try to open a project file on the desktop of my imac. I had switched to FireWire 800 lead from 400 connection that I'd used previously to the external hard disc where the assets are. Another project file using Firewire 400 opens fine with the assets etc on the same ext disc. Same thing happened before when the ext hard disc was not on and I opened a file from my desktop. it didn't matter that time. It does now. Help, advice etc appreciated.