Black Border on CR2 images

Almost all Canon raw files have masked pixels (black borders). They are cropped in raw black/white point module. The settings for this are found in cameras.xml so you will need to check what it says about your Canon model.

This post may help you Measure black and white levels? - #11 by Peter

Edit: I checked your 50D. Seems right in cameras.xml and 50D works with my 4.6.0

  1. Check your local cameras.xml
  2. Reset raw black/white point module.