Can you send me a link to one of your RW2 files?
I have the same problem, has this been resolved? I would be happy to provide a RW2 file. I'm using Lightroom 3 to convert RW2 to DNG.
Which software and version are you using to try to read the DNGs?
Um, I guess I'd have to say that it's the OS X Finder (Snow Leopard 10.6.11) and Preview.
Try choosing an older DNG compatibility version (e.g., 4.6) in the preferences. And try unchecking the "Embed Fast Load Data" option.
(The Finder and Preview don't currently support DNG 1.3 specification, and may be mistaking the fast load data as raw image data.)