Why does iMovie remove the last half of my imported clips?

I've noticed that when I'm importing clips from an SD card the window tells me "___ minutes and ___ seconds have been imported from ___ clips." but when I go to view said footage, only the first half of the each clip is there. Literally to the second, iMovie stops at exactly the halfway point of the clip and just completely removes the last half. What's going on? Please help.