The current version of the DNG Profile Editor can't deal with lossy compressed DNGs. I don't think it has any problems with fast load data. So, if you make a simple DNG with no lossy compression the current editor should be fine. As far as I know, there will be an update for the DNG Profile Editor to deal with lossy DNGs in the near future.
Not wanting to disagree with the oracle of all things LR
, but my understanding is that the profile editor will not work with a DNG that uses the profiles that have the new DNG 1.4 tags - e.g., the offset tag (don't know what the official name is) as described here: http://forums.adobe.com/message/4083472#4083472
, and also in one of my blog posts here: http://chromasoft.blogspot.com/2011/12/adobe-lr-36-and-v4-profiles-oh-dear.html
So I don't think its just a matter of lossy compressed/not.
However, I wasn't really being completely accurate about what will/won't work - actually, LR3.6 DNGs may not work either - what you really need to do is to set for DNG 1.3 compatibility when converting, rather than rely on LR versions.