The DNG specification is one that has been developed by Adobe. It is open source, any company can adopt it. However, it is up to those companies to make that decision. More and more software companies are supporting DNG, but not all. I don't believe it is a problem related to 10.4.11, but rather a problem with the other software programs that you mention.
(1) I'd think that if Adobe makes a XYZ to DNG converter for MAC OS X the goal would would that the following can open such a DNG file
(a) All Adobe Apps ..... it works ....... mission accomplished
(b) The native DNG viewer in OS X which is "Preview" .... it does not work!!!
Note: the above works if XYZ is Canons RAW. If it is coming from a Panasonic LX3 one is out of luck
(2) I just tried the above with LR 2.6RC and DNG Converter 5.6. Nothing has changed.
Anybody having an idea? work around?
I would think that the issue that you have with the LX3 DNG is that LX3 DNGs use DNG 1.2 opcodes in order to do lens corrections. So far as I am aware, Apple's raw conversion software cannot deal with opcodes. In fact, I don't think that anything other than Adobe software can deal with DNG 1.2 opcodes.
Your best bet is probably to set DNG 1.1 compatibility in DNG converter. You do that in Preferences->Compatability->Custom->Backward Version. However, if you do that, you lose corrections for lens distortion. You couls also also try setting Linear (Demosaiced) to on, which would get the lens corrections back, but I', pretty sure Apple's conversion software won't like a linear DNG any more than it likes a DNG 1.2 file.