According to the canon specs, the a590 should be able to record up to 4gb in a single file, while the s3 is limited to 1g or 1 hour, whichever comes first.
So the S3 is functioning as it should, while the a590 is definitely not. Do you see a red ! before the a590 shuts down ? If so, that means your card isn't keeping up, or you've set the video overrides too high. You can try reducing compression (using the video override settings) or resolution (using canon options). Or get a faster card.