Well, the 'read' speed of the card doesn't really matter -- just write. And even then, the method that manufacturers use to rate their card write speed is not very realistic. It's like car manufacturers rating an MPG like this: "50 MPG (when going downhill, with no passengers, nitroglycerin fuel, and gale-force winds at your back. Your mileage may vary.)" The speed in real life situations is usually less.


That said, 5.5 MB/s is not a very high write speed, and even low end cards should be able to keep up. Furthermore, it should only happen when the card buffer warning icon starts to fill up on the LCD -- if you didn't see that then it probably wasn't the card's fault. If there really are dropped frames in the video file, I think the most likely cause is a software bug.