Your drive may very well read RAM disks. (The Pioneer Drives in the G5 Towers do) but the Mac OS doesn't recognize the file format of RAMs. There is a little patch called Read!DVD that patches the OS to read them. You can get it online at <http://www.softarch.com/> It's a $40 download, but they promise to refund it if it doesn't work for you. I did a lot of experimenting with porting DVD files from a Panny stand-alone to my Mac about a year ago, and posted a long thread discussing what worked and what didn't over at the Mac forum on Videohelp.com
That said, I don't do it any more. I was mainly burning keeper copies of HD down-converts from HBO, and while I figured out methods that work using RAM disks, they were tedious, and there were a lot of irritating little problems with time code breaks and such. Now that DVD-R blanks are down to around 20 cents each, I just do a high-speed dub from the Panny's hard disk to a -R, copy that to my Mac for re-setting the widescreen flag and such and then burn a new disk. IMHO throwing away a 20 cent disk is easier than all the little hassles of working with RAM disks.