iPhoto 9.5 not uploading videos from my HD camera

I have iPhoto 9.5 and a Canon 60d camera. I used to be able to upload videos with no problem, but now I often (but not always) get a message that says "Error Downloading Image. IPhoto cannot import your photos because there was a problem downloading an image." I bought a new SD card as well as a USB-SD reader. The only thing I haven't done was upgrade iPhoto, which doesn't make sense to me since I used to be able to upload with no problem. Please help.