Problems with Soundtrack Pro 3

[Caro75]

Living in France, I usually work with Pal video but this time I have edited on an NTSC project, but when I send it to Soundtrack in order to do the mixing, my external hard disk on which is the project takes 20 minutes before beeing ready to work. The multicolored real turns and turns again, and if I try to make a crossfade, it blocks the application. I have made many tries, checks (all sounds are in 48khz, aiff or wav (no MP3). I think it might be because I have converted PAL images into NTSCs ? Has someone any idea ? Thanks.