See Through Preview Pane???

Something weird has started to happen recently with my iMovie. I connect my Panasonic Camcorder to the computer (as I've always done), I open iMovie and choose New Project (as I've always done) and then press play (as I've always done) , choose DV Format (as I've always done) but eight out of ten times when I do this nowadays, either iMovie closes "unexpectedly" or the preview pane is opaque meaning I can see my desktop wallpaper through the iMovie app preview window, strangely though, the imported footage is fine. anyone else had this problem and found a cure? Thanks