Artifacts in T3i Footage?

Hi, I was wondering if anyone could shed some light on some weird problems I've been having with T3i footage. I bought the camera (used) recently and shot a short film to test it out. The footage all looks great when played back on the camera, but after I import it onto my computer weird glitches and artifacts show up here and there in some of the clips, like in the attached screenshot.

I import the footage by dragging the entire contents of the SD card to a new folder in the Finder. The same thing happens if I import to my desktop or an external hard drive. My computer is relatively fast and recent (MacBook Pro 2.9 GHz with 8GB of RAM) so I don't think it's struggling to read the files. The artifacts persist throughout my workflow-- after I change the files to Apple ProRes in Compressor and import them into Final Cut, and still show up in clips I export from Final Cut.

I'm using the 16GB SanDisk class-10 "HD Video" SD card that came with the camera, and format it before every use. The firmware is up-to-date.

Does anyone know what could be causing this? Should I buy a new memory card, or is there potentially a problem with the camera? The problems are infrequent enough that I can cut around them for right now, but I want to fix this before I start my next project. Thanks!

The camera is fine, try to play the video directly on your tv or download the latest codecs for your PC player. Good luck!

I use the same camera and memory card, rarely take videos but never had this problem. I would take the above advice off Ispriluc.

Welcome to POTN by the way

Thanks for the welcome and the advice! I unfortunately don't have a TV to test it with, but I believe all the codecs I have are up-to-date-- at least my QuickTime is the newest version and I've installed the Pro Apps updates for Final Cut, etc. Is there an additional H.264 codec I should look for?