This has nothing to do with Canon changing something that Adobe doesn’t know how to deal with. The data in the raw files, that should be a copy of what was in the camera sensor, has become corrupted due to something outside of LR.
Corruption can be in the files, themselves, and be permanent, or it could be due to a memory fault on your computer that only shows up when you try to process the image data in some software, like LR but not part of the raw-data, itself. Since the images also looked bad on another person’s computer that indicates the data is corrupt in the image files, and probably permanent, so your recourse is to download or recover the raw files from the card again, or retrieve the raw files from a backup copy you may have made when you first offloaded the images.
As far as Canon’s recommendation to use their software, if the corruption is in the raw files, themselves, then the images will likely look bad in Canon’s DPP software if you actually create a JPG from the raw image. DPP initially just shows you the camera-embedded preview, and only works with the raw data when you’re actually creating a JPG from the raw file. Here is how you can test using Canon’s software on Windows 7:
Start -> All Programs -> Canon Utilities -> Digital Photo Professional x.xx
Locate the folder with the corrupted images in DPP’s folder view so you have thumbnails at the right.
Click on the thumbnail of a corrupted image—the thumbnail should look ok because it is just the camera-embedded preview.
In the DPP menus do File / Convert and Save…
Select a JPG format and choose a name that doesn’t conflict with any existing files.
Click the Save button and a progress window should come up. On my version there is an Error Log button. Press that and wait.
If the raw data is corrupted, eventually the Save operation will abort prematurely and you’ll see something about a decoding error in the Error Log area. This decoding error indicates there was a problem with the raw data in the file.