I have the same problem. I can get a little bit further than 30 seconds, but once the problem shows itself, I can't watch any more EHD recordings. If I reboot the EHD or the 622, I buy another 2 - 4 minutes of EHD viewing before the next lockup. I guess I have to make that call for the replacement.
Two of mine have rings and two have bars ... all work fine. However, I did get one with a bar that did not work out of the box and had to exchange it for another. Just like with anything else these days, sometimes you get a lemon.
I have a 320gb and 500gb My Book and both work well. They are the older, no frills unit with the circle as shown above. To avoid problems I never leave them on or in the 622's usb ports. When I want to archive, I plug the unit to the 622's front usb and they turn on automatically. When I'm done I simply take remove the usb cable.
Right now I am archiving a couple HD movies to a new device, it is a Simpletech SP-U35, 500gb EHD. I bought it the other day on Amazon during a sale for $99 and free shipping (I think it is currrently $114 and free shipping which is still a good deal). It seems to be taking the transfers fine but we shall see if playback is problem free. A few others have tried this drive and have had no complaints. It comes in colors (I have black and it is sleek and cool looking). It even has a blue circle on the face that tells you how much storage is left.
I opened mine and salvaged the disk. Pry it open slowly, removing the outer cover just like a book cover. Don't pry out too far. Run a knife or screwdriver all around it. The "cover" will peel off and from that point on it will be obvious. No screws on the outer case, plenty inside. I could have reassembled mine, but since the electronics were what failed, I saved the disk and tossed the rest.
BTW, that inner circle is supposed to be the power switch. Sometimes it works, sometimes not.